README file for course project

for Coursera: Getting and Cleaning Data

(by Jeff Leek, PhD, Roger D. Peng, PhD, Brian Caffo, PhD)

Repo Contents

This repo contains a script run_analysis.R which takes all of the data (contained in the data directory which is ignored in the git repo), extracts only the mean and std. dev. measurements, and puts them into a new, tidy data set, which is then stored as a text file (tab delimited) tidy_data.txt. This text file is included in the repo. The repo also includes a codebook.md file describing all the variables in the tidy_data.txt file.

Script run_analysis.R

This script loads data from the data directory and turns it into a tidy data set. It then uses that tidy data set to calculate the averages over each variable for each person/activity combo.

Reading in Data

In order to read data in use the following command

read.table("tidy_data.txt")

Notes

The columns which were included in the tidy data set include all those which were means and standard deviations. In particular, those names of features were taken which contained mean(), std(), and meanFreq().

Output

The output dataset is described in the codebook.md file.

Project Description (from course website)

The purpose of this project is to demonstrate your ability to collect, work with, and clean a data set. The goal is to prepare tidy data that can be used for later analysis. You will be graded by your peers on a series of yes/no questions related to the project. You will be required to submit: 1) a tidy data set as described below, 2) a link to a Github repository with your script for performing the analysis, and 3) a code book that describes the variables, the data, and any transformations or work that you performed to clean up the data called CodeBook.md. You should also include a README.md in the repo with your scripts. This repo explains how all of the scripts work and how they are connected.

One of the most exciting areas in all of data science right now is wearable computing - see for example this article . Companies like Fitbit, Nike, and Jawbone Up are racing to develop the most advanced algorithms to attract new users. The data linked to from the course website represent data collected from the accelerometers from the Samsung Galaxy S smartphone. A full description is available at the site where the data was obtained:

http://archive.ics.uci.edu/ml/datasets/Human+Activity+Recognition+Using+Smartphones

Here are the data for the project:

https://d396qusza40orc.cloudfront.net/getdata%2Fprojectfiles%2FUCI%20HAR%20Dataset.zip

You should create one R script called run_analysis.R that does the following.

1. Merges the training and the test sets to create one data set.
2. Extracts only the measurements on the mean and standard deviation for each measurement.
3. Uses descriptive activity names to name the activities in the data set
4. Appropriately labels the data set with descriptive variable names.
5. From the data set in step 4, creates a second, independent tidy data set with the average of each variable for each activity and each subject.