tiagodsilva / programmingassignment

Programming assignment of the course "Getting and Cleaning Data" (Johns Hopkins Data Science Specialization).

ProgrammingAssignment

Programming assignment of Getting and Cleaning Data. This assignment consists in cleaning the data of this experiment, which can be downloaded at this site. The orignal README contains a lot of information about the data.

The code book contain informations about the tables in output.

In summary, this is the description of the original file:

Original files:

The original file contains 10299 measurements (one-per-row) divided in two sets:
	- train (7352)
	- test (2947)
	
Each measurement is a vector with 561-entries in the interval [-1, 1].

For each row, there is an associated subject and an activiy, which are described below:

- Subject
	Description: Number between 1 and 30 that identifies the subject
	Type: integer
- Activity
	Description: Name of the activity realized by the subject
	Type: categoric
	Values:
		1 - WALKING
		2 - WALKING_UPSTAIRS
		3 - WALKING_DOWNSTAIRS
		4 - SITTING
		5 - STANDING
		6 - LAYING

Descriptions of the scripts

I put a lot of commentaries in the code, so it can be readable. After I loaded the values with the read.table() function, I took the transpose of the data frame; since each row corresponds to a measurement, that is a nice way to calculate the mean and the standard deviation. Then, the columns' names were changed (so they corresponde to each activity), which has been followed by the merging of the training data and the test data with the cbind() function. With those tables, I used a for loop to calculate the mean and the standard deviation for each column. To finalize the task, I included, again with cbind(), the subject for each measurement. All this information is available in the script. The final table, as is written in the code book, has the following description:

File: summary_values_subject

COLUMNS:

- Subject
	Description: Number between 1 and 30 that identifies the subject
	Type: integer

- Activity
	Description: Name of the activity realized by the subject
	Type: categoric
	Values:
		WALKING
		WALKING_UPSTAIRS
		WALKING_DOWNSTAIRS
		SITTING
		STANDING
		LAYING
		
- Mean
	Description: Mean of the measurements made, normalized and bounded within [-1,1]
	Type: numeric

- Standard_Deviation
	Description: Standard deviation of the measurements made, normalized and bounded within [-1, 1]
	Type: numeric