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Code Book for Samsung Data

Context

This is the codebook for the Getting and Cleaning Data Course Project.

The input data for the project can be found here:

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

The data is also checked into this repository in the "UCI HAR Dataset" subdirectory, in case it is changed or deleted on the web.

Raw Data

For a description of the underlying data collection and format, please reference the README.txt file in the UCI HAR Dataset subdirectory.

Tidy Data (part 1)

The project is in two parts. Part one is to tidy up the raw accelerometer data, in the following steps:

  • 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 variable names.

to perform these steps, do the following in R:

    library(dplyr)
    source("run_analysis.R")
    tidyData <- getTidyData()

Variables

The tidy data variables are as follows:

Subject: The participant subject identifier, range 1-30.

Activity: The activity classification, one of WALKING, WALKING_UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING

Measurement columns: a subset of the raw data measurements that includes the mean and standard deviation measurements only. These are in the form XXX-std() and YYY-mean(). The meaning of these measurements can be found in the raw data subdirectory in the features_info.txt file.

Output data (part 2)

Part two is to perform the following:

  • From the data set in part 1, creates a second, independent tidy data set with the average of each variable for each activity and each subject.

to perform this steps, execute the following R function (in "run_analysis.R") on the tidy data set created in part 1, to create the output.txt output file:

    outputDataSet <- createOutputDataSet(tidyData)
    writeDataSet(outputDataSet)

Variables

The output data variables are as follows:

Subject: The participant subject identifier, range 1-30.

Activity: The activity classification, one of WALKING, WALKING_UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING

Measurement columns: the mean of all observations of the original mean and standard deviation measurements. These are in the form "XXX-std()" and "YYY-mean()". Understanding the meaning of these summary measurements is not a goal of this project.