This file describes how run_analysis.R script works.
* First, unzip the data from https://d396qusza40orc.cloudfront.net/getdata%2Fprojectfiles%2FUCI%20HAR%20Dataset.zip and rename the folder with "data".
* Make sure the folder "data" and the run_analysis.R script are both in the current working directory.
* Second, use source("run_analysis.R") command in RStudio.
* Third, you will find an output file generated in the current working directory: data_with_means.txt. It contains a data frame.
* Finally, use data <- read.table("data_with_means.txt") command in RStudio to read the file. Since we are required to get the average of each variable for each activity and each subject, and there are 6 activities in total and 30 subjects in total, we have 180 rows with all combinations for each of the 66 features.