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Code Book for TidyData from Human Activity Recognition Using Smartphones Dataset

Variables from 3 to 81 consist on average of mean and standard deviation measurements from the "Human Activity Recognition Using Smartphones Data Set".

According to the study description, this variables from 3 to 81 can be read corresponding to the next description:

"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"

Variables

1 "subject"

Subject identificator: 1 to 30 (number of participants in the original study)

2 "activity"

Activity identificator:

1 walking

2 walking_upstair

3 walking_dowstairs

4 sitting

5 standing

6 laying

3 "tBodyAccmeanX"

4 "tBodyAccmeanY"

5 "tBodyAccmeanZ"

6 "tBodyAccstdX"

7 "tBodyAccstdY"

8 "tBodyAccstdZ"

9 "tGravityAccmeanX"

10 "tGravityAccmeanY"

11 "tGravityAccmeanZ"

12 "tGravityAccstdX"

13 "tGravityAccstdY"

14 "tGravityAccstdZ"

15 "tBodyAccJerkmeanX"

16 "tBodyAccJerkmeanY"

17 "tBodyAccJerkmeanZ"

18 "tBodyAccJerkstdX"

19 "tBodyAccJerkstdY"

20 "tBodyAccJerkstdZ"

21 "tBodyGyromeanX"

22 "tBodyGyromeanY"

23 "tBodyGyromeanZ"

24 "tBodyGyrostdX"

25 "tBodyGyrostdY"

26 "tBodyGyrostdZ"

27 "tBodyGyroJerkmeanX"

28 "tBodyGyroJerkmeanY"

29 "tBodyGyroJerkmeanZ"

30 "tBodyGyroJerkstdX"

31 "tBodyGyroJerkstdY"

32 "tBodyGyroJerkstdZ"

33 "tBodyAccMagmean"

34 "tBodyAccMagstd"

35 "tGravityAccMagmean"

36 "tGravityAccMagstd"

37 "tBodyAccJerkMagmean"

38 "tBodyAccJerkMagstd"

39 "tBodyGyroMagmean"

40 "tBodyGyroMagstd"

41 "tBodyGyroJerkMagmean"

42 "tBodyGyroJerkMagstd"

43 "fBodyAccmeanX"

44 "fBodyAccmeanY"

45 "fBodyAccmeanZ"

46 "fBodyAccstdX"

47 "fBodyAccstdY"

48 "fBodyAccstdZ"

49 "fBodyAccmeanFreqX"

50 "fBodyAccmeanFreqY"

51 "fBodyAccmeanFreqZ"

52 "fBodyAccJerkmeanX"

53 "fBodyAccJerkmeanY"

54 "fBodyAccJerkmeanZ"

55 "fBodyAccJerkstdX"

56 "fBodyAccJerkstdY"

57 "fBodyAccJerkstdZ"

58 "fBodyAccJerkmeanFreqX"

59 "fBodyAccJerkmeanFreqY"

60 "fBodyAccJerkmeanFreqZ"

61 "fBodyGyromeanX"

62 "fBodyGyromeanY"

63 "fBodyGyromeanZ"

64 "fBodyGyrostdX"

65 "fBodyGyrostdY"

66 "fBodyGyrostdZ"

67 "fBodyGyromeanFreqX"

68 "fBodyGyromeanFreqY"

69 "fBodyGyromeanFreqZ"

70 "fBodyAccMagmean"

71 "fBodyAccMagstd"

72 "fBodyAccMagmeanFreq"

73 "fBodyBodyAccJerkMagmean"

74 "fBodyBodyAccJerkMagstd"

75 "fBodyBodyAccJerkMagmeanFreq"

76 "fBodyBodyGyroMagmean"

77 "fBodyBodyGyroMagstd"

78 "fBodyBodyGyroMagmeanFreq"

79 "fBodyBodyGyroJerkMagmean"

80 "fBodyBodyGyroJerkMagstd"

81 "fBodyBodyGyroJerkMagmeanFreq"