Skip to content

Latest commit

 

History

History
126 lines (115 loc) · 4 KB

CodeBook.md

File metadata and controls

126 lines (115 loc) · 4 KB
Raw

Code book

The original data consists 561 features. A detailed description of the data can be fouund in features_info.txt in the dataset zip file.

From the original data set the following feature description is taken:

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.

  • tBodyAcc-XYZ
  • tGravityAcc-XYZ
  • tBodyAccJerk-XYZ
  • tBodyGyro-XYZ
  • tBodyGyroJerk-XYZ
  • tBodyAccMag
  • tGravityAccMag
  • tBodyAccJerkMag
  • tBodyGyroMag
  • tBodyGyroJerkMag
  • fBodyAcc-XYZ
  • fBodyAccJerk-XYZ
  • fBodyGyro-XYZ
  • fBodyAccMag
  • fBodyAccJerkMag
  • fBodyGyroMag
  • fBodyGyroJerkMag

The following subset of variables that were estimated from these signals that were used are:

  • mean(): Mean value
  • std(): Standard deviation

#Processing of data sets

The raw dataset was filtered to limit the set to the mean and std values using the following regular expression:

mean\\(\\)|std\\(\\)

The resulting columns were made tidy by removing the following characters '-','(' and ')'. The string 'std' and 'mean' were replaced by 'Std' and 'Mean'. Finally the substring 'BodyBody' was replaced by 'Body'. This resulted in the following list of variables.

#Variables The complete list of variables is shown below.

  • Subject id of the subject
  • Activity measured activity (WALKING, WALKING_UPSTAIRS, WALKING_DOWNSTAIRS, SITTING, STANDING, LAYING)
  • tBodyAccMeanX
  • tBodyAccMeanY
  • tBodyAccMeanZ
  • tBodyAccStdX
  • tBodyAccStdY
  • tBodyAccStdZ
  • tGravityAccMeanX
  • tGravityAccMeanY
  • tGravityAccMeanZ
  • tGravityAccStdX
  • tGravityAccStdY
  • tGravityAccStdZ
  • tBodyAccJerkMeanX
  • tBodyAccJerkMeanY
  • tBodyAccJerkMeanZ
  • tBodyAccJerkStdX
  • tBodyAccJerkStdY
  • tBodyAccJerkStdZ
  • tBodyGyroMeanX
  • tBodyGyroMeanY
  • tBodyGyroMeanZ
  • tBodyGyroStdX
  • tBodyGyroStdY
  • tBodyGyroStdZ
  • tBodyGyroJerkMeanX
  • tBodyGyroJerkMeanY
  • tBodyGyroJerkMeanZ
  • tBodyGyroJerkStdX
  • tBodyGyroJerkStdY
  • tBodyGyroJerkStdZ
  • tBodyAccMagMean
  • tBodyAccMagStd
  • tGravityAccMagMean
  • tGravityAccMagStd
  • tBodyAccJerkMagMean
  • tBodyAccJerkMagStd
  • tBodyGyroMagMean
  • tBodyGyroMagStd
  • tBodyGyroJerkMagMean
  • tBodyGyroJerkMagStd
  • fBodyAccMeanX
  • fBodyAccMeanY
  • fBodyAccMeanZ
  • fBodyAccStdX
  • fBodyAccStdY
  • fBodyAccStdZ
  • fBodyAccJerkMeanX
  • fBodyAccJerkMeanY
  • fBodyAccJerkMeanZ
  • fBodyAccJerkStdX
  • fBodyAccJerkStdY
  • fBodyAccJerkStdZ
  • fBodyGyroMeanX
  • fBodyGyroMeanY
  • fBodyGyroMeanZ
  • fBodyGyroStdX
  • fBodyGyroStdY
  • fBodyGyroStdZ
  • fBodyAccMagMean
  • fBodyAccMagStd
  • fBodyAccJerkMagMean
  • fBodyAccJerkMagStd
  • fBodyGyroMagMean
  • fBodyGyroMagStd
  • fBodyGyroJerkMagMean
  • fBodyGyroJerkMagStd