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Code Book

Human Activity Recognition Using Smartphones Dataset

Each record provides:

  • Mean or standard deviation of Triaxial acceleration from the accelerometer (total acceleration) and the estimated body acceleration.
  • Mean or standard deviation of Triaxial Angular velocity from the gyroscope.
  • Its activity label.
  • An identifier of the subject who carried out the experiment.

Experimental Study Design

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.

Feature Selection

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.

This data consists of the means and standard deviations of the experimental data. Feature Descriptions

The following lists the features included in the file produced, a description of each and measurement units

  1. activity --- One of six activities performed
  2. subjectID --- ID of the subject who performed the activity
  3. time-bodyacceleration-mean-X --- Mean body acceleration time - X direction --- standard gravity units, 'g'
  4. time-bodyacceleration-mean-Y --- Mean body acceleration time - Y direction --- standard gravity units, 'g'
  5. time-bodyacceleration-mean-Z --- Mean body acceleration time - Z direction --- standard gravity units, 'g'
  6. time-bodyacceleration-stdev-X --- Stdev of time of body acceleration - X direction --- standard gravity units, 'g'
  7. time-bodyacceleration-stdev-Y --- Stdev of time of body acceleration - Y direction --- standard gravity units, 'g'
  8. time-bodyacceleration-stdev-Z --- Stdev of time of body acceleration - Z direction --- standard gravity units, 'g'
  9. time-gravityacceleration-mean-X --- Mean gravity acceleration time - X direction --- standard gravity units, 'g'
  10. time-gravityacceleration-mean-Y --- Mean gravity acceleration time - Y direction --- standard gravity units, 'g'
  11. time-gravityacceleration-mean-Z --- Mean gravity acceleration time - Z direction --- standard gravity units, 'g'
  12. time-gravityacceleration-stdev-X --- Stdev of time of gravity accelerationleration - X direction --- standard gravity units, 'g'
  13. time-gravityacceleration-stdev-Y --- Stdev of time of gravity accelerationleration - Y direction --- standard gravity units, 'g'
  14. time-gravityacceleration-stdev-Z --- Stdev of time of gravity accelerationleration - Z direction --- standard gravity units, 'g'
  15. time-bodyaccelerationJerk-mean-X --- Mean body acceleration jerk time - X direction --- standard gravity units, 'g'
  16. time-bodyaccelerationJerk-mean-Y --- Mean body acceleration jerk time - Y direction --- standard gravity units, 'g'
  17. time-bodyaccelerationJerk-mean-Z --- Mean body acceleration jerk time - Z direction --- standard gravity units, 'g'
  18. time-bodyaccelerationJerk-stdev-X --- Stdev of time of body acceleration jerk - X direction --- standard gravity units, 'g'
  19. time-bodyaccelerationJerk-stdev-Y --- Stdev of time of body acceleration jerk - Y direction --- standard gravity units, 'g'
  20. time-bodyaccelerationJerk-stdev-Z --- Stdev of time of body acceleration jerk - Z direction --- standard gravity units, 'g'
  21. time-bodyangularvelocity-mean-X --- Mean body gyroscope measurement - X direction --- radians/second
  22. time-bodyangularvelocity-mean-Y --- Mean body gyroscope measurement - Y direction --- radians/second
  23. time-bodyangularvelocity-mean-Z --- Mean body gyroscope measurement - Z direction --- radians/second
  24. time-bodyangularvelocity-stdev-X --- Stdev of body gyroscope measurement - X direction --- radians/second
  25. time-bodyangularvelocity-stdev-Y --- Stdev of body gyroscope measurement - Y direction --- radians/second
  26. time-bodyangularvelocity-stdev-Z --- Stdev of body gyroscope measurement - Z direction --- radians/second
  27. time-bodyangularvelocity-mean-X --- Mean jerk signal of body - X direction --- standard gravity units, 'g'
  28. time-bodyangularvelocity-mean-Y --- Mean jerk signal of body - Y direction --- standard gravity units, 'g'
  29. time-bodyangularvelocity-mean-Z --- Mean jerk signal of body - Z direction --- standard gravity units, 'g'
  30. time-bodyangularvelocity-stdev-X --- Stdev of jerk signal of body - X direction --- standard gravity units, 'g'
  31. time-bodyangularvelocity-stdev-Y --- Stdev of jerk signal of body - Y direction --- standard gravity units, 'g'
  32. time-bodyangularvelocity-stdev-Z --- Stdev of jerk signal of body - Z direction --- standard gravity units, 'g'
  33. time-bodyaccelerationmagnitude-mean --- Mean magnitude of body acceleration --- Euclidean norm
  34. time-bodyaccelerationmagnitude-stdev --- Stdev of body acceleration magnitude --- Euclidean norm
  35. time-gravityaccelerationmagnitude-mean --- Mean gravity acceleration magnitude --- Euclidean norm
  36. time-gravityaccelerationmagnitude-stdev --- Stdev of gravity acceleration magnitude --- Euclidean norm
  37. time-bodyaccelerationJerkmagnitude-mean --- Mean magnitude of body acceleration jerk --- standard gravity units, 'g'
  38. time-bodyaccelerationJerkmagnitude-stdev --- Stdev of magnitude of body acceleration jerk --- standard gravity units, 'g'
  39. time-bodyangularvelocitymagnitude-mean --- Mean magnitude of body gyroscope measurement --- radians/second
  40. time-bodyangularvelocitymagnitude-stdev --- Stdev of magnitude of body gyroscope measurement --- radians/second
  41. time-bodyangularvelocitymagnitude-mean --- Mean magnitude of body gyroscope jerk measurement --- radians/second
  42. time-bodyangularvelocitymagnitude-stdev --- Stdev of magnitude of body gyroscope jerk measurement --- radians/second
  43. freq-bodyacceleration-mean-X --- Mean frequency of body acceleration - X direction --- FFT of standard gravity units
  44. freq-bodyacceleration-mean-Y --- Mean frequency of body acceleration - Y direction --- FFT of standard gravity units
  45. freq-bodyacceleration-mean-Z --- Mean frequency of body acceleration - Z direction --- FFT of standard gravity units
  46. freq-bodyacceleration-stdev-X --- Stdev of frequency of body acceleration - X direction --- FFT of standard gravity units
  47. freq-bodyacceleration-stdev-Y --- Stdev of frequency of body acceleration - Y direction --- FFT of standard gravity units
  48. freq-bodyacceleration-stdev-Z --- Stdev of frequency of body acceleration - Z direction --- FFT of standard gravity units
  49. freq-bodyaccelerationJerk-mean-X --- Mean frequency of body acceleration jerk - X direction --- FFT of standard gravity units
  50. freq-bodyaccelerationJerk-mean-Y --- Mean frequency of body acceleration jerk - Y direction --- FFT of standard gravity units
  51. freq-bodyaccelerationJerk-mean-Z --- Mean frequency of body acceleration jerk - Z direction --- FFT of standard gravity units
  52. freq-bodyaccelerationJerk-stdev-X --- Stdev of frequency of body acceleration jerk - X direction --- FFT of standard gravity units
  53. freq-bodyaccelerationJerk-stdev-Y --- Stdev of frequency of body acceleration jerk - Y direction --- FFT of standard gravity units
  54. freq-bodyaccelerationJerk-stdev-Z --- Stdev of frequency of body acceleration jerk - Z direction --- FFT of standard gravity units
  55. freq-bodyangularvelocity-mean-X --- Mean frequency of body gyroscope measurement - X direction --- FFT of standard gravity units
  56. freq-bodyangularvelocity-mean-Y --- Mean frequency of body gyroscope measurement - Y direction --- FFT of standard gravity units
  57. freq-bodyangularvelocity-mean-Z --- Mean frequency of body gyroscope measurement - Z direction --- FFT of standard gravity units
  58. freq-bodyangularvelocity-stdev-X --- Stdev of frequency of body gyroscope measurement - X direction --- FFT of standard gravity units
  59. freq-bodyangularvelocity-stdev-Y --- Stdev of frequency of body gyroscope measurement - Y direction --- FFT of standard gravity units
  60. freq-bodyangularvelocity-stdev-Z --- Stdev of frequency of body gyroscope measurement - Z direction --- FFT of standard gravity units
  61. freq-bodyaccelerationmagnitude-mean --- Mean frequency of body acceleration magnitude --- Euclidean norm
  62. freq-bodyaccelerationmagnitude-stdev --- Stdev of frequency of body acceleration magnitude --- Euclidean norm
  63. freq-bodybodyaccelerationJerkmagnitude-mean --- Mean frequency of body acceleration jerk magnitude --- Euclidean norm
  64. freq-bodybodyaccelerationJerkmagnitude-stdev --- Stdev of frequency of body acceleration jerk magnitude --- Euclidean norm
  65. freq-bodybodyangularvelocitymagnitude-mean --- Mean frequency of magnitude of body gyroscope measurement --- Euclidean norm
  66. freq-bodybodyangularvelocitymagnitude-stdev --- Stdev of frequency of magnitude of body gyroscope measurement --- Euclidean norm
  67. freq-bodybodyangularvelocitymagnitude-mean --- Mean frequency of magnitude of body gyroscope jerk measurement --- Euclidean norm
  68. freq-bodybodyangularvelocitymagnitude-stdev --- Stdev of frequency of magnitude of body gyroscope jerk measurement --- Euclidean norm

Notes:

  • Features are normalized and bounded within [-1,1].

License:

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.