data_cleaning

data cleaning course from Coursera of John Hopkins

run_analysis.R:

this script process the dataset downloaded from

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

according to the instructions from Getting and Cleaning Data Course Project.

files should not moved after unzipping the zip file, and this script work only in the unchanged, unzipped folder of the zip file

Step 1: load all data sets in the memory,

    features.txt: indicate what each column is for each data set
    
    activity_labels.txt: indicate which number stand for which activity
    
    y_train.txt & y_test.txt: indicate the activity for each row, 
                              converted from number to descriptive names,
                              as indicated in activity_labels.txt

        X_train.txt & X_test.txt: the data sets

    subject_train.txt & subject_test.txt: indicate the subject for each row

Step 2: label/append the data sets with varible names, subjects, activities

Step 3: subset the data sets which are means and standard deviations

     use grep to get features which are means and standard deviations

Step 4: bind the data sets

Step 5: Get the means for each variable for each subject and each activity

     split data frame according to subject and activity
     
     use lapply to subset and get average of each column
     
     change list back to the data frame
     
     append Subjects and Activities back to the data frame
     
     label the columns properly

Step 6: save the table into ZF_Submission.txt

code book.txt:

describe the names of the variables in ZF_Submission.txt

ZF_Submission.txt

the processed clean data set

README.md

this file