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MATLAB CHEATSHEETS
Kevin Patel edited this page Apr 9, 2020
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1 revision
- Read Image File
%%
% replace `PATH_TO_IMAGE` with actual image file path
%
impath = 'PATH_TO_IMAGE';
%%
% read image
%
img = imread(impath);
- Write Image
%%
% write image
%
imwrite(img,'new_image_filename.jpg');
- Show Image
%%
% show image
%
imshow(img);
%%
% display multiple image in same window
%
subplot(1,2,1),imshow(img1);
title('First Image');
subplot(1,2,2),imshow(img2);
title('Second Image');
%%
% using figure
%
figure;
imshow(img);
- Dimensions of Image
%%
% get the dimensions of image
% if img is colour image then dimension is vector with 3 elements
% if img is grayscale image then dimension is vector wit 2 dimensions
%
dimensions = size(img);
% number of rows
nr = dimensions(1);
% number of columns
nc = dimensions(2);
- Image Type Conversion (Color Scale Conversion)
%%
% Convert RGB image to colormap to gray scale image
%
imgray = rgb2gray(imrgb);
%%
% Convert grayscale or binary image to indexed image
%
imind = gray2ind(imgray);
%%
% Convert matrix to grayscale image
%
imgray = mat2gray(A); % where A is a 2D matrix
%%
% Split multichannel image into its individual channels
% eg. if you read an rgb image it has 3 color channel Red, Green & Blue
% if one need to fetch individual channel from that you can use the following funtion
%
[ r, g, b ] = imsplit(imrgb); % r contains red channel of image; g contains green channnel of image; b contains blue channel of image;
- Graphs & Plots
%%
% histogram plot of the gray scale image file
%
imhist(imgray);
%%
% bar chart
%
X = [100,200,300,400,500,600,700]
Y = [3,6,9,12,15,18,21]
% plot X vs Y plot
bar(X,Y);
% plot X
bar(X)
%%
% line plot
%
X = linspace(-2*pi,2*pi,100);
Y = sin(X);
plot(X,Y); % plots X vs sin(X) plot
subplot(1,3,3),plot(X,Y1,X,Y2); % plots X vs sin(X) AND X vs cos(X) plot
%%
% Customize your plot
%
% give title of the plot
bar(X,Y);
title('My Data Plot');
% change the color of the plots
% ------------------------------------------------------------------
% | Short Name | Color Name | RGB Triplet | Hexadecimal Color Code |
% ------------------------------------------------------------------
% | 'r' | 'red' | [1 0 0] | '#FF0000' |
% | 'g' | 'green' | [0 1 0] | '#00FF00' |
% | 'b' | 'blue' | [0 0 1] | '#0000FF' |
% | 'c' | 'cyan' | [0 1 1] | '#00FFFF' |
% | 'm' | 'magenta' | [1 0 1] | '#FF00FF' |
% | 'k' | 'black' | [1 1 0] | '#FFFF00' |
% | 'w' | 'white' | [0 0 0] | '#000000' |
% | 'y' | 'yellow' | [1 1 1] | '#FFFFFF' |
% ------------------------------------------------------------------
bar(X,'r'); % this plots red coloured bar graph
% plot X vs sin(X) AND X vs cos(X) plots
X = linspace(-2*pi,2*pi,100);
Y1 = sin(X);
Y2 = cos(X);
plot(X,Y1,X,Y2);
% give label to the plot
xlabel('-2\pi < X < 2\pi');
ylabel('Sine and Cosine Values');
% add legend to the plot
legend({'y = sin(x)','y = cos(x)'},'Location','northeast');
% change line style of the line graph
% -------------------------------------------
% | Value | Description |
% -------------------------------------------
% | '--' | Dashed line |
% | '-' | Solid line (default) |
% | ':' | Dotted line |
% | '-.' | Dash-dot line |
% -------------------------------------------
plot(X,Y1,'--'); % change line style to dashed line
% change line markers of the line graph
% -------------------------------------------
% | Value | Description |
% -------------------------------------------
% | 'o' | Circle |
% | '+' | Plus sign |
% | 'x' | Cross |
% | '*' | Asterisk |
% | '.' | Dot |
% | 's' | Square |
% | 'd' | Diamond |
% | 'p' | Pentagram (Five pointed star) |
% | 'h' | Hexagram (Six pointed star) |
% | '>' | Right pointing triangle |
% | '<' | Left pointing triangle |
% | '^' | Upward pointing triangle |
% | 'v' | Downward pointing triangle |
% -------------------------------------------
plot(X,Y1,'o'); % this shows the line in the form of sequence of small circles
% combine multiple properties in one
% shows dashed line with circle in red for sine plot and dashed line with cross in blue for cosine plot
plot(X,Y1,'--or',X,Y2,'--xb');
- Declare Function
function [return_values1,...,return_valuesN] = function_name(parameter1,...,parameterN)
%%
% Body Here
%%
end
- For Loop
% for loop from 1 - n
for i = 1:n
%%
% Body Here
%%
endfor
- While Loop
while condition
%%
% Body Here
%%
endwhile
- If Condition
if condition
%%
% Body Here
%%
endif
- Arithmatic Operations
%%
% Addition
%
a = 3 + 5;
%%
% Subtraction
%
a = 3 - 5;
%%
% Multiplication
%
a = 3 * 5;
%%
% Division
%
a = 3 / 5;
%%
% Power
%
a = 3 ^ 5;
% OR
a = power(3,5);
%%
% Logarithm
%
% Natural Log
a = log(3);
% Common Log
a = log10(3);
%%
% Square Root
%
a = sqrt(9);
- Bitwise Logical Operations
%%
% Logical - OR
%
a = bitor(3,5);
%%
% Logical - AND
%
a = bitand(3,5);
%%
% Logical - NOT
%
a = bitnot(3,5);
%%
% Logical - XOR
%
a = bitxor(3,5);
- Matrix Operations
%%
% Declare Column Vector
%
mat = [1; 2; 3];
%%
% Declare Row Vector
%
mat = [1 2 3];
% OR
mat = [1, 2, 3];
%%
% Declare Matrix of m x n dimension
%
% 1 2 3
% 4 5 6
% 7 8 9
%
mat = [1 2 3; 4 5 6; 7 8 9];
% OR
mat = [1, 2, 3; 4, 5, 6; 7, 8, 9];
%%
% Fetch Elements From Matrix
%
% Fetch single element
a = mat(1,1);
% OR
a = mat(1); % numerical indexing starting from 1 in column major order
% Fetch whole column
a = mat(:,1);
% Fetch whole row
a = mat(1,:);
% Fetch perticular part from matrix
a = mat(1:2,2:3);
%%
% Find Dimension of Matrix
%
dimension = size(mat);
%%
% Declare Matrix with 1
%
% 1 0 0
% 0 1 0
% 0 0 1
%
i_mat = eye(3);
% OR
i_mat = eye(3,3);
%%
% Declare Matrix with 1
%
% 1 1 1
% 1 1 1
% 1 1 1
%
i_mat = ones(3);
% OR
i_mat = ones(3,3);
%%
% Declare Matrix with 0
%
% 0 0 0
% 0 0 0
% 0 0 0
%
z_mat = zeros(3);
% OR
z_mat = zeros(3,3);
%%
% Declare Magic Matrix
%
% 8 1 6
% 3 5 7
% 4 9 2
%
magic_mat = magic(3);
%%
% Addition Operation on Matrix
%
% Add scalar value to an matrix
new_mat = mat + 2; % new_mat & mat are two matrix of m x n size
% Add matrix A with matrix B
new_mat = A + B; % new_mat, A & B are same dimension m x n matrix
%%
% Multiplication Operation on Matrix
%
% Multiply scalar value with matrix
new_mat = mat * 2;
% Multiply matrix A with matrix B
new_mat = A * B; % dimension of matrix A: m1 x n | dimension of matrix B: n x m2 | dimension of matrix new_mat: m1 x m2
% Multiply the corresponding elements of two matrices or vectors using the .* operator
new_mat = A .* B; % dimension of matrix A: m1 x n | dimension of matrix B: n x m2 | dimension of matrix new_mat: m1 x m2
%%
% Subtraction Operation on Matrix
%
% Subtract scalar value to an matrix
new_mat = mat - 2; % new_mat & mat are two matrix of m x n size
% Subtract matrix A with matrix B
new_mat = A - B; % new_mat, A & B are same dimension m x n matrix
%%
% Minimum Value
%
% Minimum of row or column vector
min_value = min(vector);
% Minimun of m x n matrix
min_value_vector = min(mat); % using min() on any matrix return vector containing minimum of each column
min_value = min(min_value_vector);
%%
% Maximum Value
%
% Maximum of row or column vector
max_value = max(vector);
% Maximun of m x n matrix
max_value_vector = max(mat); % using max() on any matrix return vector containing maximum of each column
max_value = max(max_value_vector);
%%
% Median Value
%
% Median of row or column vector
median_value = median(vector);
% Median of m x n matrix
median_value_vector = median(mat); % using median() on any matrix return vector containing median of each column
median_value = median(median_value_vector);