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Code Book

#Brief Description TidyData.txt contains the following columns:

  • SubjectID: The unique integer ID of the subject from whom various measurements is taken.
  • Activity: The type of activity the subject was undertaking.
  • FeatureName: The name of the feature that was measured.
  • FeatureStatistic: The type of statistical measure performed on the observations of each feature for each SubjectID and Activity.
  • FeatureAverage: The average value over all observations of each feature for a given SubjectID, Activity.

#Variables

##Subject ID Unique ID of each subject

type: int values: 1 to 30

##Activity Activity that each subject perfomed. The activities performed are self explanatory

type: factor values: WALKING, WALKING_UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING

##Feature Statistic The statistical measure performed on observations of each feature

type: factor values: mean, std

mean - the mean value of each feature for a given activity and subject std - the standard deviation of each feature for a given activity and subject

##Feature Average The average value of observations of each feature for a given subject and activity

type: double values: bound between [-1,1] (since the data is bound between -1 and 1)

##Feature Names The name of the feature that is measured

type: string values: see description below

The feature names follow a logical naming format, the names can be disected into a few parts.

  1. t/f: Measurement is in the Time domain (t) or Frequency domain (f)
  2. Body/Gravity: Measurement is of either Body or Gravity
  3. Acc/Gyro: Measurement is either from Accelerometer (Acc) or Gyroscope (Gyro)
  4. Jerk/(empty): Can be empty. If its not empty, 'Jerk' is change in the given feature over time, for example ..AccJerk.. is the change in acceleration over time.
  5. -X/-Y/-Z/Mag: Measurement is from the X axis (-X) or Y axis (-Y) or Z axis (-Z)

units:

  • Accelerometer: m/s/s
  • Accelerometer Jerk: m/s/s/s
  • Gyroscope: rad/s
  • Gyroscope Jerk: rad/s/s

Note: since the values are generally in [-1,1] I assume that at least the acceleration must have been normalized by gravity (9.8 m/s/s)