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 'time' 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 'frequency' 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.
timeBodyAcc-XYZ timeGravityAcc-XYZ timeBodyAccJerk-XYZ timeBodyGyro-XYZ timeBodyGyroJerk-XYZ timeBodyAccMag timeGravityAccMag timeBodyAccJerkMag timeBodyGyroMag timeBodyGyroJerkMag frequencyBodyAcc-XYZ frequencyBodyAccJerk-XYZ frequencyBodyGyro-XYZ frequencyBodyAccMag frequencyBodyAccJerkMag frequencyBodyGyroMag frequencyBodyGyroJerkMag
The set of variables that were estimated from these signals are:
mean: Mean value std: Standard deviation meanFreq: Weighted average of the frequency components to obtain a mean frequency angle: Angle between to vectors.
Additional vectors obtained by averaging the signals in a signal window sample. These are used on the angle() variable:
gravityMean tBodyAccMean tBodyAccJerkMean tBodyGyroMean tBodyGyroJerkMean
Below is a complete list of the variables included in the datasets
[1] "subjectid"
[2] "activity"
[3] "timebodyaccmeanx"
[4] "timebodyaccmeany"
[5] "timebodyaccmeanz"
[6] "timebodyaccstdx"
[7] "timebodyaccstdy"
[8] "timebodyaccstdz"
[9] "timegravityaccmeanx"
[10] "timegravityaccmeany"
[11] "timegravityaccmeanz"
[12] "timegravityaccstdx"
[13] "timegravityaccstdy"
[14] "timegravityaccstdz"
[15] "timebodyaccjerkmeanx"
[16] "timebodyaccjerkmeany"
[17] "timebodyaccjerkmeanz"
[18] "timebodyaccjerkstdx"
[19] "timebodyaccjerkstdy"
[20] "timebodyaccjerkstdz"
[21] "timebodygyromeanx"
[22] "timebodygyromeany"
[23] "timebodygyromeanz"
[24] "timebodygyrostdx"
[25] "timebodygyrostdy"
[26] "timebodygyrostdz"
[27] "timebodygyrojerkmeanx"
[28] "timebodygyrojerkmeany"
[29] "timebodygyrojerkmeanz"
[30] "timebodygyrojerkstdx"
[31] "timebodygyrojerkstdy"
[32] "timebodygyrojerkstdz"
[33] "timebodyaccmagmean"
[34] "timebodyaccmagstd"
[35] "timegravityaccmagmean"
[36] "timegravityaccmagstd"
[37] "timebodyaccjerkmagmean"
[38] "timebodyaccjerkmagstd"
[39] "timebodygyromagmean"
[40] "timebodygyromagstd"
[41] "timebodygyrojerkmagmean"
[42] "timebodygyrojerkmagstd"
[43] "frequencybodyaccmeanx"
[44] "frequencybodyaccmeany"
[45] "frequencybodyaccmeanz"
[46] "frequencybodyaccstdx"
[47] "frequencybodyaccstdy"
[48] "frequencybodyaccstdz"
[49] "frequencybodyaccmeanfreqx"
[50] "frequencybodyaccmeanfreqy"
[51] "frequencybodyaccmeanfreqz"
[52] "frequencybodyaccjerkmeanx"
[53] "frequencybodyaccjerkmeany"
[54] "frequencybodyaccjerkmeanz"
[55] "frequencybodyaccjerkstdx"
[56] "frequencybodyaccjerkstdy"
[57] "frequencybodyaccjerkstdz"
[58] "frequencybodyaccjerkmeanfreqx"
[59] "frequencybodyaccjerkmeanfreqy"
[60] "frequencybodyaccjerkmeanfreqz"
[61] "frequencybodygyromeanx"
[62] "frequencybodygyromeany"
[63] "frequencybodygyromeanz"
[64] "frequencybodygyrostdx"
[65] "frequencybodygyrostdy"
[66] "frequencybodygyrostdz"
[67] "frequencybodygyromeanfreqx"
[68] "frequencybodygyromeanfreqy"
[69] "frequencybodygyromeanfreqz"
[70] "frequencybodyaccmagmean"
[71] "frequencybodyaccmagstd"
[72] "frequencybodyaccmagmeanfreq"
[73] "frequencybodybodyaccjerkmagmean"
[74] "frequencybodybodyaccjerkmagstd"
[75] "frequencybodybodyaccjerkmagmeanfreq"
[76] "frequencybodybodygyromagmean"
[77] "frequencybodybodygyromagstd"
[78] "frequencybodybodygyromagmeanfreq"
[79] "frequencybodybodygyrojerkmagmean"
[80] "frequencybodybodygyrojerkmagstd"
[81] "frequencybodybodygyrojerkmagmeanfreq"
[82] "angletbodyaccmeangravity"
[83] "angletbodyaccjerkmeangravitymean"
[84] "angletbodygyromeangravitymean"
[85] "angletbodygyrojerkmeangravitymean"
[86] "anglexgravitymean"
[87] "angleygravitymean"
[88] "anglezgravitymean"