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CodeBook.md

This codebook provides additional information related to this project / repo.

Data sources

A full and detailed description of the data is available from: http://archive.ics.uci.edu/ml/datasets/Human+Activity+Recognition+Using+Smartphones

Note: The data for this project was provided from: https://d396qusza40orc.cloudfront.net/getdata%2Fprojectfiles%2FUCI%20HAR%20Dataset.zip The data is assumed to be unzipped into the same working directory as the script run_analysis.R.

Data sets used

The data sets are described in detail in the 'features_info.txt' and 'README.txt' files included with the data. A summary is provided below.

Data used/manipulated in the script are:

Labels (the list of features and activities)

1- 'features.txt': List of features (described in features_info.txt).

2- 'activity_labels.txt': Links the activity id labels with their activity name.

Training Data

3- 'train/X_train.txt': Training set.

4- 'train/y_train.txt': Training labels.

5- 'train/subject_train.txt': Each row identifies the subject who performed the activity.

Test Data

6- 'test/X_test.txt': Test set.

7- 'test/y_test.txt': Test labels.

8- 'test/subject_test.txt': Each row identifies the subject who performed the activity.

Two tidy data sets were generated:

1- "merged_mean_std_data.txt" This file combines the rows of the training and test data sets:

 'train/X_train.txt' rows plus 'test/X_test.txt' rows
 
 'train/y_train.txt' rows plus 'test/y_test.txt' rows
 
 'train/subject_train.txt' rows plus 'test/subject_test.txt' rows

Punctuation was removed from the 'features.txt' labels and the activity ids were replaced with descriptive activity labels in y_data

Then a subset of 'features.txt' labels is used to select only the columns that include "Mean", "mean" OR "std" as part of the feature label, namely:

			1	 --	tBodyAccmeanX
			2	 --	tBodyAccmeanY
			3	 --	tBodyAccmeanZ
			4	 --	tBodyAccstdX
			5	 --	tBodyAccstdY
			6	 --	tBodyAccstdZ
			7	 --	tGravityAccmeanX
			8	 --	tGravityAccmeanY
			9	 --	tGravityAccmeanZ
			10	 --	tGravityAccstdX
			11	 --	tGravityAccstdY
			12	 --	tGravityAccstdZ
			13	 --	tBodyAccJerkmeanX
			14	 --	tBodyAccJerkmeanY
			15	 --	tBodyAccJerkmeanZ
			16	 --	tBodyAccJerkstdX
			17	 --	tBodyAccJerkstdY
			18	 --	tBodyAccJerkstdZ
			19	 --	tBodyGyromeanX
			20	 --	tBodyGyromeanY
			21	 --	tBodyGyromeanZ
			22	 --	tBodyGyrostdX
			23	 --	tBodyGyrostdY
			24	 --	tBodyGyrostdZ
			25	 --	tBodyGyroJerkmeanX
			26	 --	tBodyGyroJerkmeanY
			27	 --	tBodyGyroJerkmeanZ
			28	 --	tBodyGyroJerkstdX
			29	 --	tBodyGyroJerkstdY
			30	 --	tBodyGyroJerkstdZ
			31	 --	tBodyAccMagmean
			32	 --	tBodyAccMagstd
			33	 --	tGravityAccMagmean
			34	 --	tGravityAccMagstd
			35	 --	tBodyAccJerkMagmean
			36	 --	tBodyAccJerkMagstd
			37	 --	tBodyGyroMagmean
			38	 --	tBodyGyroMagstd
			39	 --	tBodyGyroJerkMagmean
			40	 --	tBodyGyroJerkMagstd
			41	 --	fBodyAccmeanX
			42	 --	fBodyAccmeanY
			43	 --	fBodyAccmeanZ
			44	 --	fBodyAccstdX
			45	 --	fBodyAccstdY
			46	 --	fBodyAccstdZ
			47	 --	fBodyAccmeanFreqX
			48	 --	fBodyAccmeanFreqY
			49	 --	fBodyAccmeanFreqZ
			50	 --	fBodyAccJerkmeanX
			51	 --	fBodyAccJerkmeanY
			52	 --	fBodyAccJerkmeanZ
			53	 --	fBodyAccJerkstdX
			54	 --	fBodyAccJerkstdY
			55	 --	fBodyAccJerkstdZ
			56	 --	fBodyAccJerkmeanFreqX
			57	 --	fBodyAccJerkmeanFreqY
			58	 --	fBodyAccJerkmeanFreqZ
			59	 --	fBodyGyromeanX
			60	 --	fBodyGyromeanY
			61	 --	fBodyGyromeanZ
			62	 --	fBodyGyrostdX
			63	 --	fBodyGyrostdY
			64	 --	fBodyGyrostdZ
			65	 --	fBodyGyromeanFreqX
			66	 --	fBodyGyromeanFreqY
			67	 --	fBodyGyromeanFreqZ
			68	 --	fBodyAccMagmean
			69	 --	fBodyAccMagstd
			70	 --	fBodyAccMagmeanFreq
			71	 --	fBodyBodyAccJerkMagmean
			72	 --	fBodyBodyAccJerkMagstd
			73	 --	fBodyBodyAccJerkMagmeanFreq
			74	 --	fBodyBodyGyroMagmean
			75	 --	fBodyBodyGyroMagstd
			76	 --	fBodyBodyGyroMagmeanFreq
			77	 --	fBodyBodyGyroJerkMagmean
			78	 --	fBodyBodyGyroJerkMagstd
			79	 --	fBodyBodyGyroJerkMagmeanFreq
			80	 --	angletBodyAccMeangravity
			81	 --	angletBodyAccJerkMeangravityMean
			82	 --	angletBodyGyroMeangravityMean
			83	 --	angletBodyGyroJerkMeangravityMean
			84	 --	angleXgravityMean
			85	 --	angleYgravityMean
			86	 --	angleZgravityMean

Finally the merged data is written to a file in the working directory

2- "mean_measures_data.txt"

This file starts with the merged data from the above steps.

The melt function is applied to create a "tall/skinny" data set.

Then the dcast function is applied that combines calculates the
corresponding means for each subject + activity combination.

Finally the means data is written to a file in the working directory