The features selected for this database come from the accelerometer and gyroscope 3-axial raw signals. These time domain signals 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 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. Also the magnitude of these three-dimensional signals were calculated using the Euclidean norm.
Finally a Fast Fourier Transform (FFT) was applied to some of these signals producing frequency domain signals.
According to the best practices about naming variables, variable names are as follows:
subject : The subject identifier
activity : The activity type
timebodyaccelerationmeanxdirection : The mean of time of the aceleration of the body in X axis direction
timebodyaccelerationmeanydirection : The mean of time of the aceleration of the body in Y axis direction
timebodyaccelerationmeanzdirection : The mean of time of the aceleration of the body in Z axis direction
timebodyaccelerationstandarddeviationxdirection : The standard deviation of time of the aceleration of the body in X axis direction
timebodyaccelerationstandarddeviationydirection : The standard deviation of time of the aceleration of the body in Y axis direction
timebodyaccelerationstandarddeviationzdirection : The standard deviation of time of the aceleration of the body in Z axis direction
timegravityaccelerationmeanxdirection : The mean of time of the aceleration of the gravity in X axis direction
timegravityaccelerationmeanydirection : The mean of time of the aceleration of the gravity in Y axis direction
timegravityaccelerationmeanzdirection : The mean of time of the aceleration of the gravity in Z axis direction
timegravityaccelerationstandarddeviationxdirection : The standard deviation of time of the aceleration of the gravity in X axis direction
timegravityaccelerationstandarddeviationydirection : The standard deviation of time of the aceleration of the gravity in Y axis direction
timegravityaccelerationstandarddeviationzdirection : The standard deviation of time of the aceleration of the gravity in Z axis direction
timebodyaccelerationjerkmeanxdirection : The jerk mean of time of the aceleration of the body in X axis direction
timebodyaccelerationjerkmeanydirection : The jerk mean of time of the aceleration of the body in Y axis direction
timebodyaccelerationjerkmeanzdirection : The jerk mean of time of the aceleration of the body in Z axis direction
timebodyaccelerationjerkstandarddeviationxdirection : The jerk standard deviation of time of the aceleration of the body in X axis direction
timebodyaccelerationjerkstandarddeviationydirection : The jerk standard deviation of time of the aceleration of the body in Y axis direction
timebodyaccelerationjerkstandarddeviationzdirection : The jerk standard deviation of time of the aceleration of the body in Z axis direction
timebodygyroscopemeanxdirection : The mean of time of the gyro of the body in X axis direction
timebodygyroscopemeanydirection : The mean of time of the gyro of the body in Y axis direction
timebodygyroscopemeanzdirection : The mean of time of the gyro of the body in Z axis direction
timebodygyroscopestandarddeviationxdirection : The standard deviation of time of the gyro of the body in X axis direction
timebodygyroscopestandarddeviationydirection : The standard deviation of time of the gyro of the body in Y axis direction
timebodygyroscopestandarddeviationzdirection : The standard deviation of time of the gyro of the body in Z axis direction
timebodygyroscopejerkmeanxdirection : The jerk mean of time of the gyro of the body in X axis direction
timebodygyroscopejerkmeanydirection : The jerk mean of time of the gyro of the body in Y axis direction
timebodygyroscopejerkmeanzdirection : The jerk mean of time of the gyro of the body in Z axis direction
timebodygyroscopejerkstandarddeviationxdirection : The jerk standard deviation of time of the gyro of the body in X axis direction
timebodygyroscopejerkstandarddeviationydirection : The jerk standard deviation of time of the gyro of the body in Y axis direction
timebodygyroscopejerkstandarddeviationzdirection : The jerk standard deviation of time of the gyro of the body in Z axis direction
timebodyaccelerationmagnitudemean : The mean of time of the magnitude of the acceleration of the body
timebodyaccelerationmagnitudestandarddeviation : The standard deviation of the magnitude of the acceleration of the body
timegravityaccelerationmagnitudemean : The mean of time of the magnitude of the acceleration of the gravity
timegravityaccelerationmagnitudestandarddeviation : The standard deviation of time of the magnitude of the acceleration of the gravity
timebodyaccelerationjerkmagnitudemean : The jerk mean of time of the magnitude of the acceleration of the body
timebodyaccelerationjerkmagnitudestandarddeviation : The jerk standard deviation of time of the magnitude of the acceleration of the body
timebodygyroscopemagnitudemean : The mean of time of the magnitude of the gyro of the body
timebodygyroscopemagnitudestandarddeviation : The standard deviation of time of the magnitude of the gyro of the body
timebodygyroscopejerkmagnitudemean : The jerk mean of time of the magnitude of the gyro of the body
timebodygyroscopejerkmagnitudestandarddeviation : The jerk standard deviation of time of the magnitude of the gyro of the body
frequencybodyaccelerationmeanxdirection : The mean of frequency of the acceleration of the body in X axis direction
frequencybodyaccelerationmeanydirection : The mean of frequency of the acceleration of the body in Y axis direction
frequencybodyaccelerationmeanzdirection : The mean of frequency of the acceleration of the body in Z axis direction
frequencybodyaccelerationstandarddeviationxdirection : The standard deviation of frequency of the acceleration of the body in X axis direction
frequencybodyaccelerationstandarddeviationydirection : The standard deviation of frequency of the acceleration of the body in Y axis direction
frequencybodyaccelerationstandarddeviationzdirection : The standard deviation of frequency of the acceleration of the body in Z axis direction
frequencybodyaccelerationjerkmeanxdirection : The jerk mean of frequency of the acceleration of the body in X axis direction
frequencybodyaccelerationjerkmeanydirection : The jerk mean of frequency of the acceleration of the body in Y axis direction
frequencybodyaccelerationjerkmeanzdirection : The jerk mean of frequency of the acceleration of the body in Z axis direction
frequencybodyaccelerationjerkstandarddeviationxdirection : The jerk standard deviation of frequency of the acceleration of the body in X axis direction
frequencybodyaccelerationjerkstandarddeviationydirection : The jerk standard deviation of frequency of the acceleration of the body in Y axis direction
frequencybodyaccelerationjerkstandarddeviationzdirection : The jerk standard deviation of frequency of the acceleration of the body in Z axis direction
frequencybodygyroscopemeanxdirection : The mean of frequency of the gyro of the body in X axis direction
frequencybodygyroscopemeanydirection : The mean of frequency of the gyro of the body in Y axis direction
frequencybodygyroscopemeanzdirection : The mean of frequency of the gyro of the body in Z axis direction
frequencybodygyroscopestandarddeviationxdirection : The standard deviation of frequency of the gyro of the body in X axis direction
frequencybodygyroscopestandarddeviationydirection : The standard deviation of frequency of the gyro of the body in Y axis direction
frequencybodygyroscopestandarddeviationzdirection : The standard deviation of frequency of the gyro of the body in Z axis direction
frequencybodyaccelerationmagnitudemean : The mean of frequency of the magnitude of the acceleration of the body
frequencybodyaccelerationmagnitudestandarddeviation : The standard deviation of frequency of the magnitude of the acceleration of the body
frequencybodybodyaccelerationjerkmagnitudemean : The jerk mean of frequency of the magnitude of the acceleration of the body
frequencybodybodyaccelerationjerkmagnitudestandarddeviation: The jerk standard deviation of frequency of the magnitude of the acceleration of the body
frequencybodybodygyroscopemagnitudemean : The mean of frequency of the magnitude of the gyro of the body
frequencybodybodygyroscopemagnitudestandarddeviation : The standard deviation of frequency of the magnitude of the gyro of the body
frequencybodybodygyroscopejerkmagnitudemean : The jerk mean of frequency of the magnitude of the gyro of the body
frequencybodybodygyroscopejerkmagnitudestandarddeviation : The jerk standard deviation of frequency of the magnitude of the gyro of the body