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Code book for tidy_set.txt

General

This document describes the variables in the tidy_set.txt file.

All variables are mean of other mean or standard deviation features in the raw data.

All variables are normalized and bounded within [-1,1].

Raw data

The raw data is available here.

Variable details

Key columns

The key columns are categorical.

Each key column pair is unique and identify a row in the tidy set. The columns are:

  • 1: subject
    • Identifier of the subject (person) who performed the activity.
    • Value range [1:30]
  • 2: activity
    • Performed activity.
    • Value set: laying, sitting, standing, walking, walking_downstairs, walking_upstairs

Variable columns

The variable columns are continuous in the interval [-1,1]. They are normalized and have no unit.

Each variable represents the mean of a feature in the raw data set, by subject and activity.

The following are the variables and the feature they are based on, in order:

  • 3: mean_time_body_accelerometer_x: Based on tBodyAcc-mean()-X.
  • 4: mean_time_body_accelerometer_y: Based on tBodyAcc-mean()-Y.
  • 5: mean_time_body_accelerometer_z: Based on tBodyAcc-mean()-Z.
  • 6: standard_deviation_time_body_accelerometer_x: Based on tBodyAcc-std()-X.
  • 7: standard_deviation_time_body_accelerometer_y: Based on tBodyAcc-std()-Y.
  • 8: standard_deviation_time_body_accelerometer_z: Based on tBodyAcc-std()-Z.
  • 9: mean_time_gravity_accelerometer_x: Based on tGravityAcc-mean()-X.
  • 10: mean_time_gravity_accelerometer_y: Based on tGravityAcc-mean()-Y.
  • 11: mean_time_gravity_accelerometer_z: Based on tGravityAcc-mean()-Z.
  • 12: standard_deviation_time_gravity_accelerometer_x: Based on tGravityAcc-std()-X.
  • 13: standard_deviation_time_gravity_accelerometer_y: Based on tGravityAcc-std()-Y.
  • 14: standard_deviation_time_gravity_accelerometer_z: Based on tGravityAcc-std()-Z.
  • 15: mean_time_body_accelerometer_jerk_x: Based on tBodyAccJerk-mean()-X.
  • 16: mean_time_body_accelerometer_jerk_y: Based on tBodyAccJerk-mean()-Y.
  • 17: mean_time_body_accelerometer_jerk_z: Based on tBodyAccJerk-mean()-Z.
  • 18: standard_deviation_time_body_accelerometer_jerk_x: Based on tBodyAccJerk-std()-X.
  • 19: standard_deviation_time_body_accelerometer_jerk_y: Based on tBodyAccJerk-std()-Y.
  • 20: standard_deviation_time_body_accelerometer_jerk_z: Based on tBodyAccJerk-std()-Z.
  • 21: mean_time_body_gyroscope_x: Based on tBodyGyro-mean()-X.
  • 22: mean_time_body_gyroscope_y: Based on tBodyGyro-mean()-Y.
  • 23: mean_time_body_gyroscope_z: Based on tBodyGyro-mean()-Z.
  • 24: standard_deviation_time_body_gyroscope_x: Based on tBodyGyro-std()-X.
  • 25: standard_deviation_time_body_gyroscope_y: Based on tBodyGyro-std()-Y.
  • 26: standard_deviation_time_body_gyroscope_z: Based on tBodyGyro-std()-Z.
  • 27: mean_time_body_gyroscope_jerk_x: Based on tBodyGyroJerk-mean()-X.
  • 28: mean_time_body_gyroscope_jerk_y: Based on tBodyGyroJerk-mean()-Y.
  • 29: mean_time_body_gyroscope_jerk_z: Based on tBodyGyroJerk-mean()-Z.
  • 30: standard_deviation_time_body_gyroscope_jerk_x: Based on tBodyGyroJerk-std()-X.
  • 31: standard_deviation_time_body_gyroscope_jerk_y: Based on tBodyGyroJerk-std()-Y.
  • 32: standard_deviation_time_body_gyroscope_jerk_z: Based on tBodyGyroJerk-std()-Z.
  • 33: mean_time_body_accelerometer_magnitude: Based on tBodyAccMag-mean().
  • 34: standard_deviation_time_body_accelerometer_magnitude: Based on tBodyAccMag-std().
  • 35: mean_time_gravity_accelerometer_magnitude: Based on tGravityAccMag-mean().
  • 36: standard_deviation_time_gravity_accelerometer_magnitude: Based on tGravityAccMag-std().
  • 37: mean_time_body_accelerometer_jerk_magnitude: Based on tBodyAccJerkMag-mean().
  • 38: standard_deviation_time_body_accelerometer_jerk_magnitude: Based on tBodyAccJerkMag-std().
  • 39: mean_time_body_gyroscope_magnitude: Based on tBodyGyroMag-mean().
  • 40: standard_deviation_time_body_gyroscope_magnitude: Based on tBodyGyroMag-std().
  • 41: mean_time_body_gyroscope_jerk_magnitude: Based on tBodyGyroJerkMag-mean().
  • 42: standard_deviation_time_body_gyroscope_jerk_magnitude: Based on tBodyGyroJerkMag-std().
  • 43: mean_frequency_body_accelerometer_x: Based on fBodyAcc-mean()-X.
  • 44: mean_frequency_body_accelerometer_y: Based on fBodyAcc-mean()-Y.
  • 45: mean_frequency_body_accelerometer_z: Based on fBodyAcc-mean()-Z.
  • 46: standard_deviation_frequency_body_accelerometer_x: Based on fBodyAcc-std()-X.
  • 47: standard_deviation_frequency_body_accelerometer_y: Based on fBodyAcc-std()-Y.
  • 48: standard_deviation_frequency_body_accelerometer_z: Based on fBodyAcc-std()-Z.
  • 49: mean_frequency_body_accelerometer_jerk_x: Based on fBodyAccJerk-mean()-X.
  • 50: mean_frequency_body_accelerometer_jerk_y: Based on fBodyAccJerk-mean()-Y.
  • 51: mean_frequency_body_accelerometer_jerk_z: Based on fBodyAccJerk-mean()-Z.
  • 52: standard_deviation_frequency_body_accelerometer_jerk_x: Based on fBodyAccJerk-std()-X.
  • 53: standard_deviation_frequency_body_accelerometer_jerk_y: Based on fBodyAccJerk-std()-Y.
  • 54: standard_deviation_frequency_body_accelerometer_jerk_z: Based on fBodyAccJerk-std()-Z.
  • 55: mean_frequency_body_gyroscope_x: Based on fBodyGyro-mean()-X.
  • 56: mean_frequency_body_gyroscope_y: Based on fBodyGyro-mean()-Y.
  • 57: mean_frequency_body_gyroscope_z: Based on fBodyGyro-mean()-Z.
  • 58: standard_deviation_frequency_body_gyroscope_x: Based on fBodyGyro-std()-X.
  • 59: standard_deviation_frequency_body_gyroscope_y: Based on fBodyGyro-std()-Y.
  • 60: standard_deviation_frequency_body_gyroscope_z: Based on fBodyGyro-std()-Z.
  • 61: mean_frequency_body_accelerometer_magnitude: Based on fBodyAccMag-mean().
  • 62: standard_deviation_frequency_body_accelerometer_magnitude: Based on fBodyAccMag-std().
  • 63: mean_frequency_body_body_accelerometer_jerk_magnitude: Based on fBodyBodyAccJerkMag-mean().
  • 64: standard_deviation_frequency_body_body_accelerometer_jerk_magnitude: Based on fBodyBodyAccJerkMag-std().
  • 65: mean_frequency_body_body_gyroscope_magnitude: Based on fBodyBodyGyroMag-mean().
  • 66: standard_deviation_frequency_body_body_gyroscope_magnitude: Based on fBodyBodyGyroMag-std().
  • 67: mean_frequency_body_body_gyroscope_jerk_magnitude: Based on fBodyBodyGyroJerkMag-mean().
  • 68: standard_deviation_frequency_body_body_gyroscope_jerk_magnitude: Based on fBodyBodyGyroJerkMag-std().

Features that are not included

Only direct mean and standard deviation variables are included from the raw data. Examples of features that are not used in the raw data set:

  • fBodyAcc-meanFreq()-X
  • fBodyAcc-meanFreq()-Y
  • fBodyAcc-meanFreq()-Z
  • fBodyAccJerk-meanFreq()-X
  • fBodyAccJerk-meanFreq()-Y
  • fBodyAccJerk-meanFreq()-Z
  • fBodyGyro-meanFreq()-X
  • fBodyGyro-meanFreq()-Y
  • fBodyGyro-meanFreq()-Z
  • fBodyAccMag-meanFreq()
  • fBodyBodyAccJerkMag-meanFreq()
  • fBodyBodyGyroMag-meanFreq()
  • fBodyBodyGyroJerkMag-meanFreq()
  • angle(tBodyAccMean,gravity)
  • angle(tBodyAccJerkMean),gravityMean)
  • angle(tBodyGyroMean,gravityMean)
  • angle(tBodyGyroJerkMean,gravityMean)
  • angle(X,gravityMean)
  • angle(Y,gravityMean)
  • angle(Z,gravityMean)

The motivation for not including them is that they appear to be based on mean variables but are not primary mean variables themselves.