The run_analysis.r script performs the actions specified in the assignment

First the data is imported. Your working directory should contain the files needed for the analysis. 

The first task in the assignment asks for one merged data set. 
It is named "fulldata" in the script

The second task asks for only the means or the standard deviations in the data set
They are names "fulldata_means" and "fulldata_sds"
If you want to have them combined in one data.frame use "mean_sd_extract"

The fifth task asks for the mean in the aggregation of the data set on the subject and activity. This is called "aggregation" in the script. Note that the variables have the prefix “mean_” to indicate the aggregation