Update CodeBook.md

Variable	Descritpion
Activity	The activity peformed.
Subject	The ID of the subject.
tBodyAcc-mean()-X	Mean time for acceleration of body for X direction.
tBodyAcc-mean()-Y	Mean time for acceleration of body for Y direction.
tBodyAcc-mean()-Z	Mean time for acceleration of body for Z direction.
tBodyAcc-std()-X	Standard deviation of time for acceleration of body for X direction.
tBodyAcc-std()-Y	Standard deviation of time for acceleration of body for Y direction.
tBodyAcc-std()-Z	Standard deviation of time for acceleration of body for Z direction.
tGravityAcc-mean()-X	Mean time of acceleration of gravity for X direction.
tGravityAcc-mean()-Y	Mean time of acceleration of gravity for Y direction.
tGravityAcc-mean()-Z	Mean time of acceleration of gravity for Z direction.
tGravityAcc-std()-X	Standard deviation of time of acceleration of gravity for X direction.
tGravityAcc-std()-Y	Standard deviation of time of acceleration of gravity for Y direction.
tGravityAcc-std()-Z	Standard deviation of time of acceleration of gravity for Z direction.
tBodyAccJerk-mean()-X	Mean time of body acceleration jerk for X direction.
tBodyAccJerk-mean()-Y	Mean time of body acceleration jerk for Y direction
tBodyAccJerk-mean()-Z	Mean time of body acceleration jerk for Z direction
tBodyAccJerk-std()-X	Standard deviation of time of body acceleration jerk for X direction.
tBodyAccJerk-std()-Y	Standard deviation of time of body acceleration jerk for Y direction.
tBodyAccJerk-std()-Z	Standard deviation of time of body acceleration jerk for Z direction.
tBodyGyro-mean()-X	Mean body gyroscope measurement for X direction.
tBodyGyro-mean()-Y	Mean body gyroscope measurement for Y direction.
tBodyGyro-mean()-Z	Mean body gyroscope measurement for Z direction.
tBodyGyro-std()-X	Standard deviation of body gyroscope measurement for X direction.
tBodyGyro-std()-Y	Standard deviation of body gyroscope measurement for Y direction.
tBodyGyro-std()-Z	Standard deviation of body gyroscope measurement for Z direction.
tBodyGyroJerk-mean()-X	Mean jerk signal of body for X direction.
tBodyGyroJerk-mean()-Y	Mean jerk signal of body for Y direction.
tBodyGyroJerk-mean()-Z	Mean jerk signal of body for Z direction.
tBodyGyroJerk-std()-X	Standard deviation of jerk signal of body for X direction.
tBodyGyroJerk-std()-Y	Standard deviation of jerk signal of body for Y direction.
tBodyGyroJerk-std()-Z	Standard deviation of jerk signal of body for Z direction.
tBodyAccMag-mean()	Mean magnitude of body Acc
tBodyAccMag-std()	Standard deviation of magnitude of body Acc
tGravityAccMag-mean()	Mean gravity acceleration magnitude.
tGravityAccMag-std()	Standard deviation of gravity acceleration magnitude.
tBodyAccJerkMag-mean()	Mean magnitude of body acceleration jerk.
tBodyAccJerkMag-std()	Standard deviation of magnitude of body acceleration jerk.
tBodyGyroMag-mean()	Mean magnitude of body gyroscope measurement.
tBodyGyroMag-std()	Standard deviation of magnitude of body gyroscope measurement.
tBodyGyroJerkMag-mean()	Mean magnitude of body body gyroscope jerk measurement.
tBodyGyroJerkMag-std()	Standard deviation of magnitude of body body gyroscope jerk measurement.
fBodyAcc-mean()-X	Mean frequency of body acceleration for X direction.
fBodyAcc-mean()-Y	Mean frequency of body acceleration for Y direction.
fBodyAcc-mean()-Z	Mean frequency of body acceleration for Z direction.
fBodyAcc-std()-X	Standard deviation of frequency of body acceleration for X direction.
fBodyAcc-std()-Y	Standard deviation of frequency of body acceleration for Y direction.
fBodyAcc-std()-Z	Standard deviation of frequency of body acceleration for Z direction.
fBodyAccJerk-mean()-X	Mean frequency of body accerlation jerk for X direction.
fBodyAccJerk-mean()-Y	Mean frequency of body accerlation jerk for Y direction.
fBodyAccJerk-mean()-Z	Mean frequency of body accerlation jerk for Z direction.
fBodyAccJerk-std()-X	Standard deviation frequency of body accerlation jerk for X direction.
fBodyAccJerk-std()-Y	Standard deviation frequency of body accerlation jerk for Y direction.
fBodyAccJerk-std()-Z	Standard deviation frequency of body accerlation jerk for Z direction.
fBodyGyro-mean()-X	Mean frequency of body gyroscope measurement for X direction.
fBodyGyro-mean()-Y	Mean frequency of body gyroscope measurement for Y direction.
fBodyGyro-mean()-Z	Mean frequency of body gyroscope measurement for Z direction.
fBodyGyro-std()-X	Standard deviation frequency of body gyroscope measurement for X direction.
fBodyGyro-std()-Y	Standard deviation frequency of body gyroscope measurement for Y direction.
fBodyGyro-std()-Z	Standard deviation frequency of body gyroscope measurement for Z direction.
fBodyAccMag-mean()	Mean frequency of body acceleration magnitude.
fBodyAccMag-std()	Standard deviation of frequency of body acceleration magnitude.
fBodyBodyAccJerkMag-mean()	Mean frequency of body acceleration jerk magnitude.
fBodyBodyAccJerkMag-std()	Standard deviation of frequency of body acceleration jerk magnitude.
fBodyBodyGyroMag-mean()	Mean frequency of magnitude of body gyroscope measurement.
fBodyBodyGyroMag-std()	Standard deviation of frequency of magnitude of body gyroscope measurement.
fBodyBodyGyroJerkMag-mean()	Mean frequency of magnitude of body gyroscope jerk measurement.