np_copies_views_reshape_ravel_flatten.ipynb

{
  "nbformat": 4,
  "nbformat_minor": 0,
  "metadata": {
    "colab": {
      "name": "np_copies_views_reshape_ravel_flatten.ipynb",
      "provenance": [],
      "collapsed_sections": [],
      "authorship_tag": "ABX9TyO6bvx3i6Cjg+BNuxwH+YV3",
      "include_colab_link": true
    },
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3"
    },
    "language_info": {
      "name": "python"
    }
  },
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "view-in-github",
        "colab_type": "text"
      },
      "source": [
        "<a href=\"https://colab.research.google.com/github/hiro106/statistics_ml_cs_learning/blob/main/np_copies_views_reshape_ravel_flatten.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 1,
      "metadata": {
        "id": "Tkjt48w3wc-p"
      },
      "outputs": [],
      "source": [
        "# https://numpy.org/doc/stable/user/basics.copies.html"
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "import numpy as np"
      ],
      "metadata": {
        "id": "JKapjVRcw6xH"
      },
      "execution_count": 2,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "source": [
        "## Indexing operations"
      ],
      "metadata": {
        "id": "gpCHJJya3J39"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "### View"
      ],
      "metadata": {
        "id": "hPMh_JiQRiQk"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "x = np.arange(10)"
      ],
      "metadata": {
        "id": "UTYy77_gwgqI"
      },
      "execution_count": 3,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "DrX_4rpuwgss",
        "outputId": "75577bf1-d57f-46f4-e204-420b6af3f196"
      },
      "execution_count": 4,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])"
            ]
          },
          "metadata": {},
          "execution_count": 4
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y = x[1:3] # creates a view"
      ],
      "metadata": {
        "id": "di5R3FkAwgvU"
      },
      "execution_count": 5,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "y"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "ATpR9hFVwgxg",
        "outputId": "6df794d8-a771-4f12-f89c-c07f8b8214c3"
      },
      "execution_count": 6,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([1, 2])"
            ]
          },
          "metadata": {},
          "execution_count": 6
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[1:3] = [10,11]"
      ],
      "metadata": {
        "id": "hcpxC7bpwg0B"
      },
      "execution_count": 7,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "OJO0hcaawg5Q",
        "outputId": "12c3ef3c-97f4-4473-8025-05e7e9af069a"
      },
      "execution_count": 8,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([ 0, 10, 11,  3,  4,  5,  6,  7,  8,  9])"
            ]
          },
          "metadata": {},
          "execution_count": 8
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "VDjgmjYMwg7h",
        "outputId": "d94c3efd-d606-4b73-b8f0-6fa425154ce2"
      },
      "execution_count": 9,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([10, 11])"
            ]
          },
          "metadata": {},
          "execution_count": 9
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y.base"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "dg-1s7Q5SbG2",
        "outputId": "3c353159-e409-4bbd-96ec-234d9bc79bec"
      },
      "execution_count": 10,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([ 0, 10, 11,  3,  4,  5,  6,  7,  8,  9])"
            ]
          },
          "metadata": {},
          "execution_count": 10
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y[0]= 5"
      ],
      "metadata": {
        "id": "1OjEurIXTXnI"
      },
      "execution_count": 11,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "oZjf0Xk8TbsB",
        "outputId": "33a74ffa-5df7-4d1c-8620-41ce9b266387"
      },
      "execution_count": 12,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([ 0,  5, 11,  3,  4,  5,  6,  7,  8,  9])"
            ]
          },
          "metadata": {},
          "execution_count": 12
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y.base is x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "RFSoM_ZqTcoC",
        "outputId": "84da35ae-4787-4a73-e319-49dbc3025a55"
      },
      "execution_count": 13,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "True"
            ]
          },
          "metadata": {},
          "execution_count": 13
        }
      ]
    },
    {
      "cell_type": "markdown",
      "source": [
        "### Copy"
      ],
      "metadata": {
        "id": "03KEVtsrR3Nq"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "x = np.arange(9)"
      ],
      "metadata": {
        "id": "bCDF2YAwQxSL"
      },
      "execution_count": 14,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "ttK5kYc9Qz9v",
        "outputId": "2ca94071-eb99-4b7e-e11f-5d2ce0397b66"
      },
      "execution_count": 15,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1, 2, 3, 4, 5, 6, 7, 8])"
            ]
          },
          "metadata": {},
          "execution_count": 15
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x = np.arange(9).reshape(3, 3)"
      ],
      "metadata": {
        "id": "_dfdB9W8xuWn"
      },
      "execution_count": 16,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "YiXxVwVnxuZu",
        "outputId": "564df112-6981-4ae3-fb06-a75bc83d184a"
      },
      "execution_count": 17,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2],\n",
              "       [3, 4, 5],\n",
              "       [6, 7, 8]])"
            ]
          },
          "metadata": {},
          "execution_count": 17
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[0]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Ka6-IOnRgs0I",
        "outputId": "2be6bda0-3f1e-4ad6-d42d-df669a179f41"
      },
      "execution_count": 18,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1, 2])"
            ]
          },
          "metadata": {},
          "execution_count": 18
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[[0, 1]]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Q02FuV5dgw23",
        "outputId": "b75f5b38-3b5f-453a-9e84-b07af02390a3"
      },
      "execution_count": 19,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2],\n",
              "       [3, 4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 19
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[0, 1]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "L9YTPvpmgxzq",
        "outputId": "6be7880e-185f-4506-a0c5-ffea9c5fab82"
      },
      "execution_count": 20,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "1"
            ]
          },
          "metadata": {},
          "execution_count": 20
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[0][2]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "z3ofseGQgyVD",
        "outputId": "524554ef-1bc9-49a0-9f5b-50a0fb21a8cb"
      },
      "execution_count": 21,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "2"
            ]
          },
          "metadata": {},
          "execution_count": 21
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[2][0]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "rI5L8_SZhRzy",
        "outputId": "cb7b6813-ce59-460f-e045-1e843a97099e"
      },
      "execution_count": 22,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "6"
            ]
          },
          "metadata": {},
          "execution_count": 22
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[0][[0,1]]"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "YSxoBajmhSMp",
        "outputId": "952aa666-3bb7-4206-cf48-dca9d9fd3790"
      },
      "execution_count": 23,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1])"
            ]
          },
          "metadata": {},
          "execution_count": 23
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "dqolEDRcgylT"
      },
      "execution_count": 23,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "y = x[[1, 2]]"
      ],
      "metadata": {
        "id": "P7nSqlMywg-a"
      },
      "execution_count": 24,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "y"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "G5FZ6NHqwhA1",
        "outputId": "96d3c8fd-7fde-44df-b8e5-e8ca04be04f7"
      },
      "execution_count": 25,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[3, 4, 5],\n",
              "       [6, 7, 8]])"
            ]
          },
          "metadata": {},
          "execution_count": 25
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y.base is None"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "QdwP8cqLwhDd",
        "outputId": "be5b5134-39e7-4347-c388-d42bdee2b31a"
      },
      "execution_count": 26,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "True"
            ]
          },
          "metadata": {},
          "execution_count": 26
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x[[1, 2]] = [[10, 11, 12], [13, 14, 15]]"
      ],
      "metadata": {
        "id": "IDNRh0nqRI_y"
      },
      "execution_count": 27,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "id": "xWV6FPVmRJJc",
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "outputId": "67240ddd-4964-465b-ee46-1f342cddcad0"
      },
      "execution_count": 28,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[ 0,  1,  2],\n",
              "       [10, 11, 12],\n",
              "       [13, 14, 15]])"
            ]
          },
          "metadata": {},
          "execution_count": 28
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y"
      ],
      "metadata": {
        "id": "ZSz_Fhq9RJWW",
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "outputId": "53735fa4-b87c-4bd8-d456-29a7c7a20bb8"
      },
      "execution_count": 29,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[3, 4, 5],\n",
              "       [6, 7, 8]])"
            ]
          },
          "metadata": {},
          "execution_count": 29
        }
      ]
    },
    {
      "cell_type": "markdown",
      "source": [
        "## Other operations"
      ],
      "metadata": {
        "id": "jISciL__vdbh"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "x = np.ones((2, 3))\n",
        "\n",
        "# https://numpy.org/doc/stable/reference/generated/numpy.ones.html"
      ],
      "metadata": {
        "id": "uuf7GMTqvdd9"
      },
      "execution_count": 30,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "x"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "mAu0C8cQvdgc",
        "outputId": "494208ec-d9f3-4375-8966-598fa4b7fb51"
      },
      "execution_count": 31,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1., 1.],\n",
              "       [1., 1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 31
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "y = x.T"
      ],
      "metadata": {
        "id": "V3t6CRCHvdjQ"
      },
      "execution_count": 32,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "y"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Bl2ceUD6vdl-",
        "outputId": "22532bc7-a88d-4371-a4f9-eaf023a07c56"
      },
      "execution_count": 33,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1.],\n",
              "       [1., 1.],\n",
              "       [1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 33
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z = y.view()"
      ],
      "metadata": {
        "id": "4FLNfqJJvdpL"
      },
      "execution_count": 34,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "z"
      ],
      "metadata": {
        "id": "wnw3_m1dRJfi",
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "outputId": "07367786-0b80-45e3-c4ed-3bde1d7f4bc4"
      },
      "execution_count": 35,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1.],\n",
              "       [1., 1.],\n",
              "       [1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 35
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z.shape"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "hA_JqaDehpVv",
        "outputId": "9dfcab36-ba78-4c77-dd88-8ed7c70ea8b5"
      },
      "execution_count": 36,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "(3, 2)"
            ]
          },
          "metadata": {},
          "execution_count": 36
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "# z.shape = 6"
      ],
      "metadata": {
        "id": "vaCDsDxEhpYY"
      },
      "execution_count": 37,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "z.reshape((2, 3))"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "EJ5Vaaimml-J",
        "outputId": "a5ddc9b4-c8bb-4cf5-f078-43d81f56fc40"
      },
      "execution_count": 38,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1., 1.],\n",
              "       [1., 1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 38
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "V3e7QUJlmmGb",
        "outputId": "657912d6-38fb-4fca-82f4-1cde7cd89a2b"
      },
      "execution_count": 39,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1.],\n",
              "       [1., 1.],\n",
              "       [1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 39
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z.reshape(-1)"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "L-29JXkjm1hN",
        "outputId": "607224ed-016a-4749-c3a4-ac5944fd82f9"
      },
      "execution_count": 40,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([1., 1., 1., 1., 1., 1.])"
            ]
          },
          "metadata": {},
          "execution_count": 40
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "0K_n7b0zm1wi",
        "outputId": "4d3ee116-703a-44df-abd4-75a3673cd53c"
      },
      "execution_count": 41,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1.],\n",
              "       [1., 1.],\n",
              "       [1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 41
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z_minus_one = z.reshape(-1)"
      ],
      "metadata": {
        "id": "FHvjGqvjn4QI"
      },
      "execution_count": 42,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "z_minus_one"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "qoD4UW-8n4TC",
        "outputId": "31a527c1-318d-42ea-d6f0-c38e10c3d1ff"
      },
      "execution_count": 43,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([1., 1., 1., 1., 1., 1.])"
            ]
          },
          "metadata": {},
          "execution_count": 43
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "z"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "-FwGbXscm5HV",
        "outputId": "45b4f93f-fe1c-420f-e4dd-f8b77576fba9"
      },
      "execution_count": 44,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[1., 1.],\n",
              "       [1., 1.],\n",
              "       [1., 1.]])"
            ]
          },
          "metadata": {},
          "execution_count": 44
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "3kDx2BiloGNg"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "WALQii-aoGQg"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "0IBJJflRoGUI"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "-KEL9q05oGWL"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "Y9b8DAG6oGY_"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "mxi71hbfoGb6"
      },
      "execution_count": 44,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "source": [
        "# Go off on a tangent"
      ],
      "metadata": {
        "id": "a7UtS238m0T3"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "## numpy.reshape"
      ],
      "metadata": {
        "id": "eoSoq9nlkmD1"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "# What is the difference between contiguous and non-contiguous arrays?\n",
        "# https://stackoverflow.com/questions/26998223/what-is-the-difference-between-contiguous-and-non-contiguous-arrays"
      ],
      "metadata": {
        "id": "YWrQj4q3hpaq"
      },
      "execution_count": 45,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "# numpy.reshape\n",
        "# https://numpy.org/doc/stable/reference/generated/numpy.reshape.html#numpy.reshape"
      ],
      "metadata": {
        "id": "moFjmmclhpdj"
      },
      "execution_count": 46,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "source": [
        "It is not always possible to change the shape of an array without copying the data. If you want an error to be raised when the data is copied, you should assign the new shape to the shape attribute of the array:"
      ],
      "metadata": {
        "id": "x-o__8U605sj"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "a = np.zeros((10, 2))"
      ],
      "metadata": {
        "id": "Hknk4vXshpgK"
      },
      "execution_count": 47,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "rgs1UOs3zS6n",
        "outputId": "58e995f3-3a86-4bb4-97ac-41f21442cf86"
      },
      "execution_count": 48,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.],\n",
              "       [0., 0.]])"
            ]
          },
          "metadata": {},
          "execution_count": 48
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "b = a.T"
      ],
      "metadata": {
        "id": "EyVSm4YezS9V"
      },
      "execution_count": 49,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "b"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "3GoeJG2ZzS_q",
        "outputId": "f1c16e94-37ec-4f5b-fedb-880ec20a7ddb"
      },
      "execution_count": 50,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],\n",
              "       [0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]])"
            ]
          },
          "metadata": {},
          "execution_count": 50
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "c = b.view()"
      ],
      "metadata": {
        "id": "ligrClHTzTCd"
      },
      "execution_count": 51,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "c"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "etZbb9OKzTFA",
        "outputId": "2676eed7-9f4b-4e25-8ce5-934d4dd8ebbc"
      },
      "execution_count": 52,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0., 0., 0., 0., 0., 0., 0., 0., 0., 0.],\n",
              "       [0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]])"
            ]
          },
          "metadata": {},
          "execution_count": 52
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "c.shape"
      ],
      "metadata": {
        "id": "tIY8OZRqhpiz",
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "outputId": "ff55d8d7-6764-4416-92db-f9e077b7a1a6"
      },
      "execution_count": 53,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "(2, 10)"
            ]
          },
          "metadata": {},
          "execution_count": 53
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "# c.shape = (20)"
      ],
      "metadata": {
        "id": "twM5GUIG0m3l"
      },
      "execution_count": 54,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "gfAWx6pj0m6X"
      },
      "execution_count": 54,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "a = np.arange(6)"
      ],
      "metadata": {
        "id": "FxYWL66ahMFv"
      },
      "execution_count": 55,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "4Jq1jG42hMIj",
        "outputId": "db52d99f-e0bf-4f90-cc5d-6cbdda200ae5"
      },
      "execution_count": 56,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1, 2, 3, 4, 5])"
            ]
          },
          "metadata": {},
          "execution_count": 56
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a.reshape((3, 2))"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "igj1_ac3hMLk",
        "outputId": "65b94d72-ec72-4cbc-c4de-9b097b82be40"
      },
      "execution_count": 57,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 57
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Ub7H6ug1hMOL",
        "outputId": "888f9872-79e2-45ff-9af6-7c2cca8565c3"
      },
      "execution_count": 58,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([0, 1, 2, 3, 4, 5])"
            ]
          },
          "metadata": {},
          "execution_count": 58
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "HuhbUbb00m82"
      },
      "execution_count": 58,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "a = np.arange(6).reshape((3, 2))"
      ],
      "metadata": {
        "id": "onKgxrNS0m_b"
      },
      "execution_count": 59,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "id": "2HU0W55GhpmF",
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "outputId": "68c9ec5c-79df-4727-bdf7-fd529861253e"
      },
      "execution_count": 60,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 60
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "c6ZxJMaERJpL"
      },
      "execution_count": 60,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "np.reshape(a, (2, 3)) # C-like index ordering"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Qmk0PTB4iQqH",
        "outputId": "90f3f72c-86fd-4004-a574-6f61329c9582"
      },
      "execution_count": 61,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2],\n",
              "       [3, 4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 61
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "qQKrtvKWiQso",
        "outputId": "bfef9264-79ef-4187-cc06-89c3581878b8"
      },
      "execution_count": 62,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 62
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "Q-dYTsOIiQwE"
      },
      "execution_count": 62,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "np.reshape(np.ravel(a), (2, 3)) # equivalent to C ravel then C reshape"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "DjNgiOB2kAWj",
        "outputId": "3b9da071-d2ad-4864-92e7-88e1b4061af2"
      },
      "execution_count": 63,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2],\n",
              "       [3, 4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 63
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "vIVvof_bkAZm",
        "outputId": "630cdf01-1402-41eb-f40c-991901ee38f7"
      },
      "execution_count": 64,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 64
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "qj6VXiBdkAcx"
      },
      "execution_count": 64,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "np.reshape(a, (2, 3), order='F')"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "JSIf5cUTkAfx",
        "outputId": "dafa2c60-2916-4070-d446-432e90d7c7be"
      },
      "execution_count": 65,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 4, 3],\n",
              "       [2, 1, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 65
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "gr4DABahkPxr",
        "outputId": "107f989f-4654-4115-ef30-e4c7daa9d398"
      },
      "execution_count": 66,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 66
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "Q6lTCwxCkP0S"
      },
      "execution_count": 66,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "np.reshape(np.ravel(a, order='F'), (2, 3), order='F')"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "baJZctnykAi6",
        "outputId": "0fbc1971-7ad7-4511-a3f9-1cc66ac1e40d"
      },
      "execution_count": 67,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 4, 3],\n",
              "       [2, 1, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 67
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "a"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "lUDK2P7YkAn0",
        "outputId": "1f4f644f-ce51-4d08-dab2-6efd94fe8890"
      },
      "execution_count": 68,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1],\n",
              "       [2, 3],\n",
              "       [4, 5]])"
            ]
          },
          "metadata": {},
          "execution_count": 68
        }
      ]
    },
    {
      "cell_type": "markdown",
      "source": [
        "## Contiguous and Not contiguous / C-like and Fortran-like"
      ],
      "metadata": {
        "id": "CvYNfXl6iQyR"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "# What is the difference between contiguous and non-contiguous arrays?\n",
        "# https://stackoverflow.com/questions/26998223/what-is-the-difference-between-contiguous-and-non-contiguous-arrays"
      ],
      "metadata": {
        "id": "aAp-HiL4k0IY"
      },
      "execution_count": 69,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "arr = np.arange(100000000).reshape(10000,10000)"
      ],
      "metadata": {
        "id": "b_vcZNFxk0LN"
      },
      "execution_count": 70,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "arr"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "Trp6cx8Qk0Np",
        "outputId": "64477008-0d65-4c32-dbc8-45ccdd5b26c0"
      },
      "execution_count": 71,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[       0,        1,        2, ...,     9997,     9998,     9999],\n",
              "       [   10000,    10001,    10002, ...,    19997,    19998,    19999],\n",
              "       [   20000,    20001,    20002, ...,    29997,    29998,    29999],\n",
              "       ...,\n",
              "       [99970000, 99970001, 99970002, ..., 99979997, 99979998, 99979999],\n",
              "       [99980000, 99980001, 99980002, ..., 99989997, 99989998, 99989999],\n",
              "       [99990000, 99990001, 99990002, ..., 99999997, 99999998, 99999999]])"
            ]
          },
          "metadata": {},
          "execution_count": 71
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "arr.shape"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "RDCpsdr1r5_E",
        "outputId": "b8830ef1-7a69-41b9-9a3b-5c8bee5ea86d"
      },
      "execution_count": 72,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "(10000, 10000)"
            ]
          },
          "metadata": {},
          "execution_count": 72
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "import datetime"
      ],
      "metadata": {
        "id": "pzti5yA7rc3B"
      },
      "execution_count": 73,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "datetime"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "8cExR_UJrfSI",
        "outputId": "676ceff1-c9cb-4247-86d0-548810df5364"
      },
      "execution_count": 74,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "<module 'datetime' from '/usr/lib/python3.7/datetime.py'>"
            ]
          },
          "metadata": {},
          "execution_count": 74
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "start_time = datetime.datetime.now()\n",
        "np.sum(arr, axis=1)\n",
        "end_time = datetime.datetime.now()\n",
        "print(end_time - start_time)"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "X2Q_Exf4rg3n",
        "outputId": "e7cd97bc-77ca-456f-cb4f-5edf9bd877c7"
      },
      "execution_count": 75,
      "outputs": [
        {
          "output_type": "stream",
          "name": "stdout",
          "text": [
            "0:00:00.105940\n"
          ]
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "start_time = datetime.datetime.now()\n",
        "np.sum(arr, axis=0)\n",
        "end_time = datetime.datetime.now()\n",
        "print(end_time - start_time)"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "iOHy8wabk0YT",
        "outputId": "efe80069-1247-4bbf-e082-fdbb65c419a1"
      },
      "execution_count": 76,
      "outputs": [
        {
          "output_type": "stream",
          "name": "stdout",
          "text": [
            "0:00:00.091421\n"
          ]
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "arr_transposed = arr.T"
      ],
      "metadata": {
        "id": "47xgzVTnk0bA"
      },
      "execution_count": 77,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "arr_transposed"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "QgZ5Mfd4k0dY",
        "outputId": "f558aef2-9509-42dc-fe5b-56230566e00f"
      },
      "execution_count": 78,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[       0,    10000,    20000, ..., 99970000, 99980000, 99990000],\n",
              "       [       1,    10001,    20001, ..., 99970001, 99980001, 99990001],\n",
              "       [       2,    10002,    20002, ..., 99970002, 99980002, 99990002],\n",
              "       ...,\n",
              "       [    9997,    19997,    29997, ..., 99979997, 99989997, 99999997],\n",
              "       [    9998,    19998,    29998, ..., 99979998, 99989998, 99999998],\n",
              "       [    9999,    19999,    29999, ..., 99979999, 99989999, 99999999]])"
            ]
          },
          "metadata": {},
          "execution_count": 78
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "IpYMLRL7sn-6"
      },
      "execution_count": 78,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "start_time = datetime.datetime.now()\n",
        "np.sum(arr_transposed, axis=1)\n",
        "end_time = datetime.datetime.now()\n",
        "print(end_time - start_time)"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "S7T4IdAok0fz",
        "outputId": "0752c8b4-373e-400c-b9cf-64d74c18b4f0"
      },
      "execution_count": 79,
      "outputs": [
        {
          "output_type": "stream",
          "name": "stdout",
          "text": [
            "0:00:00.084384\n"
          ]
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "start_time = datetime.datetime.now()\n",
        "np.sum(arr_transposed, axis=0)\n",
        "end_time = datetime.datetime.now()\n",
        "print(end_time - start_time)"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "k3b2TduBsj6K",
        "outputId": "3b5081e4-9545-4ff3-e2d2-3edd92c9f525"
      },
      "execution_count": 80,
      "outputs": [
        {
          "output_type": "stream",
          "name": "stdout",
          "text": [
            "0:00:00.100797\n"
          ]
        }
      ]
    },
    {
      "cell_type": "markdown",
      "source": [
        "## numpy.ravel"
      ],
      "metadata": {
        "id": "lZsXAI-6sj9d"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "\n",
        "https://numpy.org/doc/stable/reference/generated/numpy.ravel.html#numpy.ravel\n"
      ],
      "metadata": {
        "id": "XN0NF5z3skBc"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "What is the fastest axis of an array?   \n",
        "https://agilescientific.com/blog/2018/12/28/what-is-the-fastest-axis-of-an-array"
      ],
      "metadata": {
        "id": "c3vwZmT6Ie21"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "https://github.com/agilescientific/notebooks/blob/master/Fastest_dimension_of_array.ipynb"
      ],
      "metadata": {
        "id": "8uOSmwyjskIt"
      }
    },
    {
      "cell_type": "markdown",
      "source": [
        "※NumPy配列ndarrayをバイナリファイル（npy, npz）で保存  \n",
        "https://note.nkmk.me/python-numpy-load-save-savez-npy-npz/"
      ],
      "metadata": {
        "id": "oU0rES_-k0iI"
      }
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "UXsOM83_D4bi"
      },
      "execution_count": 80,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "BbLGWfTED4eI"
      },
      "execution_count": 80,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "PyD-2ZirD4gr"
      },
      "execution_count": 80,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "doKSLuexD4kI"
      },
      "execution_count": 80,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "bgTOYETCD4m7"
      },
      "execution_count": 80,
      "outputs": []
    }
  ]
}