Description

The requirements are:

• Merges the training and the test sets to create one data set.
• Extracts only the measurements on the mean and standard deviation for each measurement
• Uses descriptive activity names to name the activities in the data set
• Appropriately labels the data set with descriptive activity names.
• Creates a second, independent tidy data set with the average of each variable for each activity and each subject.

Functions

merge_data which will handle the the 1st, 3rd, and 4th requirements extract_mean_std which will handle the 2nd, 3rd, and 4th requirements melt_data_and_write_tidy_set which will handle the 5th requirement and write out the tidy set file

A helper function read_tidy_set is provided to read the generated tidy_set inside R.

merge_data

Purpose: to merge all the data from the various text files into a single giant data table. No subset or extractions performed on the data set once merged.

Parameters: directory: a character vector that indicates the folder residing inside the working directory

Value: all_data: a merged data table containing training and test data and 3 additional columns for subject, activity, and activity id. This amounts to 10299 observations of 564 variables

extract_mean_std

Purpose: Performs subset on the giant data set of merged data to extract just the mean and std related data

Parameters: data_set: a data table containing the training set and test set data and 3 additional columns for subject, activity, and activity id directory: a character vector that indicates the folder residing inside the working directory

Value: extracted_data_set: after performing subset on the data_set parameter, this is a data table that contains just 10299 observations of 69 variables basically the same 3 additional columns of subject, activity, and activity id plus the 66 columns whose headers contain the characters mean() and std()

melt_data_and_write_tidy_set

Purpose: Performs melt data, casting back to tidy data format, and then writing the data out to a text file

Parameters: extracted_mean_std_data_set: a data table containing the training set and test set data and 3 additional columns for subject, activity, and activity id but has already extracted out the mean and std columns path_to_tidyset_file: a character vector that indicates the path to write the tidy set file to

Value: nil

read_tidy_set

Purpose: Reads the tidy set file back into data table

Parameters: path_to_tidyset_file: a character vector that indicates the path to the tidy set file

Value: datatable of data inside the tidy set file