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get_project_data.R
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get_project_data.R
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################################################################################
# WHAT YOU SHOULD KNOW BEFORE EXECUTING THIS SCRIPT, 'get_project_data.R'
################################################################################
# DESCRIPTION: This script downloads and extracts the 'UCI HAR Dataset'
# in the working directory if the folder doesn't exists.
# DOWNLOAD URL:
# "https://d396qusza40orc.cloudfront.net/getdata%2Fprojectfiles%2FUCI%20HAR%20Dataset.zip"
# PLAN: Checks if the data files are available.
# If the data don't exist,
# 1. downloads the zipped file
# 2. creates a log file,
# with the url used and the date of the download
# 3. extracts the zipped file
# else if the data files exist,
# 1. informs that the files already exist
# NOTES: When 'get_project_data.R' is executed,
# informative messages are printed in console,
# to describe what the script tries to do.
################################################################################
# Downloads and unzips the 'UCI HAR Dataset'
################################################################################
## Checks if the folder 'UCI HAR Dataset' (this is the default name) exists
## in the working directory.
## * if the folder doesn't exists,
## 1. downloads the zipped files as 'data.zip',
## in the working directory
## 2. creates a log to store the download url and date,
## with name 'log.txt' in the working directory
## 3. extracts the zipped files in a folder with
## the default name 'UCI HAR Dataset', in the working directory
# Checks if the folder 'UCI HAR Dataset' already exists in the working directory
message("Searching for folder 'UCI HAR Dataset' in the working directory...")
if (!dir.exists("UCI HAR Dataset")) {
# ONE EXTREME COINCIDENCE
## It does a simplistic test, yet sufficient on most of the cases,
## that is to check if a folder with name 'UCI HAR Dataset' exists
## in the working directory to determine if it should download the files.
## Obviously if you have, by luck or on purpose, a folder with that name,
## it will mistakenly assume that it contains the correct data files.
message(" ...no folder with name 'UCI HAR Dataset'",
" exists in the working directory.")
# Downloads the needed zipped files
message("Trying to download the zipped file...")
data_url = paste0("https://d396qusza40orc.cloudfront.net/",
"getdata%2Fprojectfiles%2FUCI%20HAR%20Dataset.zip")
download.file(data_url, "data.zip")
message(" ...zipped data was downloaded successfully ",
" in the working directory as 'data.zip'.")
# Creates a log to to store
# the url used for the download and the date when the download happened
log_entry_url <- paste0("Data was downloaded from the url: ", data_url)
log_entry_date <- paste0("Data was downloaded at date: " , date())
log_con <- file("log.txt")
writeLines(c(log_entry_url, log_entry_date), log_con)
close(log_con)
message("A file was created as 'log.txt' at the working directory \n",
"which stores the url and the date, \n",
"from which zipped data files where downloaded.")
# Extracts files from zipped file 'data.zip'
message("Trying to extract files from the 'data.zip'",
"in the working directory...")
unzip("data.zip")
message(" ...data files extracted successfully, in the folder \n",
" with name 'UCI HAR Dataset' in the working directory.")
} else {
message(" ...data files are available, in the folder \n",
" with name 'UCI HAR Dataset' in the working directory.")
}
# THE END ######################################################################