The code book consists of the following:
- Table of Contents
- Informations on 'tidy_data_summary' data table
- Identificators and averages of features
- Description for the variables of 'tidy_data_summary'
- How to load 'tidy_data_summary' in R
- About 'tidy_data_summary' table
- The process by which the 'tidy_data_summary' table was produced
- Description of the features on which the averages were based
- Informations on how the features were produced from the raw data
- Informations on the collection of raw data
- About the original data set
- License
The first 2 variables, 'subject' and 'activity', can uniquely identify each row of the table. The rest 66 variables, are the averages for some selected features, those which contain informations on means and standard deviations, from the original dataset: 'Human Activity Recognition Using Smartphones Dataset Version 1.0'.
The following table describes all variables of the 'tidy_data_summary' table.
| Index | Variables | Class | Range | Description |
|---|---|---|---|---|
| 1 | subject | integer | 1 - 30 | Identifies the human subject. |
| 2 | activity | factor | 1 - 6 | Identifies the activity. Labels: WALKING, WALKING UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING |
| 3 | Avrg-tBodyAcc-mean()-X | numeric | [-1, 1] | Time domain, Average of means for body acceleration on X axis. |
| 4 | Avrg-tBodyAcc-mean()-Y | numeric | [-1, 1] | Time domain, Average of means for body acceleration on Y axis. |
| 5 | Avrg-tBodyAcc-mean()-Z | numeric | [-1, 1] | Time domain, Average of means for body acceleration on Z axis. |
| 6 | Avrg-tBodyAcc-std()-X | numeric | [-1, 1] | Time domain, Average of standard deviations for body acceleration on X axis. |
| 7 | Avrg-tBodyAcc-std()-Y | numeric | [-1, 1] | Time domain, Average of standard deviations for body acceleration on Y axis. |
| 8 | Avrg-tBodyAcc-std()-Z | numeric | [-1, 1] | Time domain, Average of standard deviations for body acceleration on Z axis. |
| 9 | Avrg-tGravityAcc-mean()-X | numeric | [-1, 1] | Time domain, Average of means for gravity acceleration on X axis. |
| 10 | Avrg-tGravityAcc-mean()-Y | numeric | [-1, 1] | Time domain, Average of means for gravity acceleration on Y axis. |
| 11 | Avrg-tGravityAcc-mean()-Z | numeric | [-1, 1] | Time domain, Average of means for gravity acceleration on Z axis. |
| 12 | Avrg-tGravityAcc-std()-X | numeric | [-1, 1] | Time domain, Average of standard deviations for gravity acceleration on X axis. |
| 13 | Avrg-tGravityAcc-std()-Y | numeric | [-1, 1] | Time domain, Average of standard deviations for gravity acceleration on Y axis. |
| 14 | Avrg-tGravityAcc-std()-Z | numeric | [-1, 1] | Time domain, Average of standard deviations for gravity acceleration on Z axis. |
| 15 | Avrg-tBodyAccJerk-mean()-X | numeric | [-1, 1] | Time domain, Average of means for the jerk of body acceleration on X axis. |
| 16 | Avrg-tBodyAccJerk-mean()-Y | numeric | [-1, 1] | Time domain, Average of means for the jerk of body acceleration on Y axis. |
| 17 | Avrg-tBodyAccJerk-mean()-Z | numeric | [-1, 1] | Time domain, Average of means for the jerk of body acceleration on Z axis. |
| 18 | Avrg-tBodyAccJerk-std()-X | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of body acceleration on X axis. |
| 19 | Avrg-tBodyAccJerk-std()-Y | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of body acceleration on Y axis. |
| 20 | Avrg-tBodyAccJerk-std()-Z | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of body acceleration on Z axis. |
| 21 | Avrg-tBodyGyro-mean()-X | numeric | [-1, 1] | Time domain, Average of means for angular velocity on X axis. |
| 22 | Avrg-tBodyGyro-mean()-Y | numeric | [-1, 1] | Time domain, Average of means for angular velocity on Y axis. |
| 23 | Avrg-tBodyGyro-mean()-Z | numeric | [-1, 1] | Time domain, Average of means for angular velocity on Z axis. |
| 24 | Avrg-tBodyGyro-std()-X | numeric | [-1, 1] | Time domain, Average of standard deviations for angular velocity on X axis. |
| 25 | Avrg-tBodyGyro-std()-Y | numeric | [-1, 1] | Time domain, Average of standard deviations for angular velocity on Y axis. |
| 26 | Avrg-tBodyGyro-std()-Z | numeric | [-1, 1] | Time domain, Average of standard deviations for angular velocity on Z axis. |
| 27 | Avrg-tBodyGyroJerk-mean()-X | numeric | [-1, 1] | Time domain, Average of means for the jerk of angular velocity on X axis. |
| 28 | Avrg-tBodyGyroJerk-mean()-Y | numeric | [-1, 1] | Time domain, Average of means for the jerk of angular velocity on Y axis. |
| 29 | Avrg-tBodyGyroJerk-mean()-Z | numeric | [-1, 1] | Time domain, Average of means for the jerk of angular velocity on Z axis. |
| 30 | Avrg-tBodyGyroJerk-std()-X | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of angular velocity on X axis. |
| 31 | Avrg-tBodyGyroJerk-std()-Y | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of angular velocity on Y axis. |
| 32 | Avrg-tBodyGyroJerk-std()-Z | numeric | [-1, 1] | Time domain, Average of standard deviations for the jerk of angular velocity on Z axis. |
| 33 | Avrg-tBodyAccMag-mean() | numeric | [-1, 1] | Time domain, Average of means for the magnitude of body acceleration. |
| 34 | Avrg-tBodyAccMag-std() | numeric | [-1, 1] | Time domain, Average of standard deviations for the magnitude of body acceleration. |
| 35 | Avrg-tGravityAccMag-mean() | numeric | [-1, 1] | Time domain, Average of means for the magnitude of gravity acceleration. |
| 36 | Avrg-tGravityAccMag-std() | numeric | [-1, 1] | Time domain, Average of standard deviations for the magnitude of gravity acceleration. |
| 38 | Avrg-tBodyAccJerkMag-mean() | numeric | [-1, 1] | Time domain, Average of means for the magnitude of jerk, of body accelaration. |
| 38 | Avrg-tBodyAccJerkMag-std() | numeric | [-1, 1] | Time domain, Average of standard deviations for the magnitude of jerk, of body accelaration. |
| 39 | Avrg-tBodyGyroMag-mean() | numeric | [-1, 1] | Time domain, Average of means for the magnitude of angular velocity. |
| 40 | Avrg-tBodyGyroMag-std() | numeric | [-1, 1] | Time domain, Average of standard deviations for the magnitude of angular velocity. |
| 41 | Avrg-tBodyGyroJerkMag-mean() | numeric | [-1, 1] | Time domain, Average of means for the magnitude of jerk, of the angular velocity. |
| 42 | Avrg-tBodyGyroJerkMag-std() | numeric | [-1, 1] | Time domain, Average of standard deviations for the magnitude of jerk, of the angular velocity. |
| 43 | Avrg-fBodyAcc-mean()-X | numeric | [-1, 1] | Frequency domain, Average of means for body acceleration on X axis. |
| 44 | Avrg-fBodyAcc-mean()-Y | numeric | [-1, 1] | Frequency domain, Average of means for body acceleration on Y axis. |
| 45 | Avrg-fBodyAcc-mean()-Z | numeric | [-1, 1] | Frequency domain, Average of means for body acceleration on Z axis. |
| 46 | Avrg-fBodyAcc-std()-X | numeric | [-1, 1] | Frequency domain, Average of standard deviations for body acceleration on X axis. |
| 47 | Avrg-fBodyAcc-std()-Y | numeric | [-1, 1] | Frequency domain, Average of standard deviations for body acceleration on Y axis. |
| 48 | Avrg-fBodyAcc-std()-Z | numeric | [-1, 1] | Frequency domain, Average of standard deviations for body acceleration on Z axis. |
| 49 | Avrg-fBodyAccJerk-mean()-X | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of the body acceleration on X axis. |
| 50 | Avrg-fBodyAccJerk-mean()-Y | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of the body acceleration on Y axis. |
| 51 | Avrg-fBodyAccJerk-mean()-Z | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of the body acceleration on Z axis. |
| 52 | Avrg-fBodyAccJerk-std()-X | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of the body acceleration on X axis. |
| 53 | Avrg-fBodyAccJerk-std()-Y | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of the body acceleration on Y axis. |
| 54 | Avrg-fBodyAccJerk-std()-Z | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of the body acceleration on Z axis. |
| 55 | Avrg-fBodyGyro-mean()-X | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of angular velocity on X axis. |
| 56 | Avrg-fBodyGyro-mean()-Y | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of angular velocity on Y axis. |
| 57 | Avrg-fBodyGyro-mean()-Z | numeric | [-1, 1] | Frequency domain, Average of means for the jerk of angular velocity on Z axis. |
| 58 | Avrg-fBodyGyro-std()-X | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of angular velocity on X axis. |
| 59 | Avrg-fBodyGyro-std()-Y | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of angular velocity on Y axis. |
| 60 | Avrg-fBodyGyro-std()-Z | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the jerk of angular velocity on Z axis. |
| 61 | Avrg-fBodyAccMag-mean() | numeric | [-1, 1] | Frequency domain, Average of means for the magnitude of body acceleration. |
| 62 | Avrg-fBodyAccMag-std() | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the magnitude of body acceleration. |
| 63 | Avrg-fBodyAccJerkMag-mean() | numeric | [-1, 1] | Frequency domain, Average of means for the magnitude of jerk, of body acceleration. |
| 64 | Avrg-fBodyAccJerkMag-std() | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the magnitude of jerk, of body acceleration. |
| 65 | Avrg-fBodyGyroMag-mean() | numeric | [-1, 1] | Frequency domain, Average of means for the magnitude of angular velocity. |
| 66 | Avrg-fBodyGyroMag-std() | numeric | [-1, 1] | Frequency domain, Average of standard deviations for the magnitude of angular velocity. |
| 67 | Avrg-fBodyGyroJerkMag-mean() | numeric | [-1, 1] | Frequency domain, Average of means for the magnitude of jerk, of angular velocity. |
| 68 | Avrg-fBodyGyroJerkMag-std() | numeric | [-1, 1] | Frequency domain, Average of standard deviation for the magnitude of jerk, of angular velocity. |
It order to load the 'tidy_data_summary' in R correctly, use the following command:
tidy_data_summary <- read.table(file = "tidy_data_summary.txt",
header = TRUE, check.names = FALSE, dec = ".")
Or for faster loading some additional arguments can be specified:
tidy_data_summary <- read.table(file = "tidy_data_summary.txt",
header = TRUE, check.names = FALSE, dec = ".",
colClasses = c("numeric", "factor", rep("numeric", 66)),
nrows = 180, comment.char = "", quote = "")
This dataset was created for the needs of:
Course 3: 'Getting and Cleaning Data', from 'Data Science Specialization', by 'Johns Hopkins University', on Coursera
The course is taught by:
- Jeff Leek, Phd
- Roger D. Peng, Phd
- Brian Caffo, Phd
The data table can be reproduced, as all required scripts are available on the Git Hub repository Getting and Cleaning Data Assignment. Before trying to reproduce it, the following notes should be taken into account:
- The data used for the download was accessed by the script 'get_project_data.R', from the url: "http://archive.ics.uci.edu/ml/datasets/Human+Activity+Recognition+Using+Smartphones" at 'Wed Jan 31 20:09:05 2018'.
- The data was then processed by the script 'run_analysis.R' to create the 'tidy_data_summary' table.
- The scripts were executed in RStudio (version 1.1.383)
- The library 'dplyr' version 0.7.4 was used.
- The output produced by 'R.version' is the following:
platform x86_64-pc-linux-gnu
arch x86_64
os linux-gnu
system x86_64, linux-gnu
status
major 3
minor 4.3
year 2017
month 11
day 30
svn rev 73796
language R
version.string R version 3.4.3 (2017-11-30)
nickname Kite-Eating Tree
In order to produce the 'tidy_data_summary' table, the script 'run_analysis.R' was created and used. It performs the following tasks:
-
Binds these files,
- UCI HAR Dataset/train/subject_train.txt
- UCI HAR Dataset/train/X_train.txt
- UCI HAR Dataset/train/y_train.txt.
from the train set by columns to a table that contains, the human subject, the activity performed and the values of the features.
-
Binds these files,
- UCI HAR Dataset/test/subject_test.txt
- UCI HAR Dataset/test/X_test.txt
- UCI HAR Dataset/test/y_test.txt.
from the test set by columns to a table that contains, the human subject, the activity performed and the values of the features.
-
Binds the data frames created for test and train set into one large dataset by rows.
- Finds the target features, which are the features with measurements about mean and standard deviation, and extracts them as well as those that indicate the 'subject' and 'activity' and creates a new data table only with the target variables.
- Replace the variable about activity, that contains integers from 1 to 6, with a factor based on levels and labels contained in the 'activity_labels' data file.
- Extracts the target variable names from 'features.txt'.
- Corrects a typo that exists in some feature names, that is to replace 'BodyBody' that appears in the names of some features with just 'Body'.
- Creates a new tidy dataset with the appropriate labels for the variable names.
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.
-
Group the tidy data table created in step 4, by 'subject' and 'activity'.
-
Summarize each variable to find the average for the grouped values.
-
Ungroup the data table.
-
Add descriptive names to the variables of the new tidy data table, by adding the prefix 'Avrg-' in the names of the target feature averages.
-
Write the data in a text file in the present working directory, by the command:
write.table(tidy_data_summary, "tidy_data_summary.txt", row.names = FALSE)
The selected features were produced, as it is explained in the 'features_info.txt' file of the original data set:
The features selected for this database come from the accelerometer and gyroscope 3-axial raw signals tAcc-XYZ and tGyro-XYZ. These time domain signals (prefix 't' to denote time) were captured at a constant rate of 50 Hz. Then they were filtered using a median filter and a 3rd order low pass Butterworth filter with a corner frequency of 20 Hz to remove noise. Similarly, the acceleration signal was then separated into body and gravity acceleration signals (tBodyAcc-XYZ and tGravityAcc-XYZ) using another low pass Butterworth filter with a corner frequency of 0.3 Hz.
Subsequently, the body linear acceleration and angular velocity were derived in time to obtain Jerk signals (tBodyAccJerk-XYZ and tBodyGyroJerk-XYZ). Also the magnitude of these three-dimensional signals were calculated using the Euclidean norm (tBodyAccMag, tGravityAccMag, tBodyAccJerkMag, tBodyGyroMag, tBodyGyroJerkMag).
Finally a Fast Fourier Transform (FFT) was applied to some of these signals producing fBodyAcc-XYZ, fBodyAccJerk-XYZ, fBodyGyro-XYZ, fBodyAccJerkMag, fBodyGyroMag, fBodyGyroJerkMag. (Note the 'f' to indicate frequency domain signals).
These signals were used to estimate variables of the feature vector for each pattern: '-XYZ' is used to denote 3-axial signals in the X, Y and Z directions.
tBodyAcc-XYZ
tGravityAcc-XYZ
tBodyAccJerk-XYZ
tBodyGyro-XYZ
tBodyGyroJerk-XYZ
tBodyAccMag
tGravityAccMag
tBodyAccJerkMag
tBodyGyroMag
tBodyGyroJerkMag
fBodyAcc-XYZ
fBodyAccJerk-XYZ
fBodyGyro-XYZ
fBodyAccMag
fBodyAccJerkMag
fBodyGyroMag
fBodyGyroJerkMagThe set of variables that were estimated from these signals are:
mean(): Mean value
std(): Standard deviation
mad(): Median absolute deviation
max(): Largest value in array
min(): Smallest value in array
sma(): Signal magnitude area
energy(): Energy measure. Sum of the squares divided by the number of values.
iqr(): Interquartile range
entropy(): Signal entropy
arCoeff(): Autorregresion coefficients with Burg order equal to 4
correlation(): correlation coefficient between two signals
maxInds(): index of the frequency component with largest magnitude
meanFreq(): Weighted average of the frequency components to obtain a mean frequency
skewness(): skewness of the frequency domain signal
kurtosis(): kurtosis of the frequency domain signal
bandsEnergy(): Energy of a frequency interval within the 64 bins of the FFT of each window.
angle(): Angle between to vectors.Additional vectors obtained by averaging the signals in a signal window sample. These are used on the angle() variable:
gravityMean
tBodyAccMean
tBodyAccJerkMean
tBodyGyroMean
tBodyGyroJerkMean
The raw singals were produced, as it is explained in the 'README.txt' file of original data set:
The experiments have been carried out with a group of 30 volunteers within an age bracket of 19-48 years. Each person performed six activities (WALKING, WALKING_UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING) wearing a smartphone (Samsung Galaxy S II) on the waist. Using its embedded accelerometer and gyroscope, we captured 3-axial linear acceleration and 3-axial angular velocity at a constant rate of 50Hz. The experiments have been video-recorded to label the data manually. The obtained dataset has been randomly partitioned into two sets, where 70% of the volunteers was selected for generating the training data and 30% the test data.
The sensor signals (accelerometer and gyroscope) were pre-processed by applying noise filters and then sampled in fixed-width sliding windows of 2.56 sec and 50% overlap (128 readings/window). The sensor acceleration signal, which has gravitational and body motion components, was separated using a Butterworth low-pass filter into body acceleration and gravity. The gravitational force is assumed to have only low frequency components, therefore a filter with 0.3 Hz cutoff frequency was used. From each window, a vector of features was obtained by calculating variables from the time and frequency domain. See 'features_info.txt' for more details.
- Triaxial acceleration from the accelerometer (total acceleration) and the estimated body acceleration.
- Triaxial Angular velocity from the gyroscope.
- A 561-feature vector with time and frequency domain variables.
- Its activity label.
- An identifier of the subject who carried out the experiment.
and also it include the following notes:
Notes:
- Features are normalized and bounded within [-1,1].
- Each feature vector is a row on the text file.
The 'tidy_data_summary' table was created by using the following data set:
Human Activity Recognition Using Smartphones Dataset Version 1.0
Jorge L. Reyes-Ortiz, Davide Anguita, Alessandro Ghio, Luca Oneto. Smartlab - Non Linear Complex Systems Laboratory DITEN - Universit? degli Studi di Genova. Via Opera Pia 11A, I-16145, Genoa, Italy. activityrecognition@smartlab.ws www.smartlab.ws
More informations about the original data set can be found here.
The following is a copy-paste from the 'README.txt' of the original data set which I encourage everybody to use.
Use of this dataset in publications must be acknowledged by referencing the following publication [1]
[1] Davide Anguita, Alessandro Ghio, Luca Oneto, Xavier Parra and Jorge L. Reyes-Ortiz. Human Activity Recognition on Smartphones using a Multiclass Hardware-Friendly Support Vector Machine. International Workshop of Ambient Assisted Living (IWAAL 2012). Vitoria-Gasteiz, Spain. Dec 2012
This dataset is distributed AS-IS and no responsibility implied or explicit can be addressed to the authors or their institutions for its use or misuse. Any commercial use is prohibited.
Jorge L. Reyes-Ortiz, Alessandro Ghio, Luca Oneto, Davide Anguita. November 2012.