The UCI HAR dataset contains numerous fields for raw accelerometer and gyroscope signals, along with a set of statistical summaries for each parameter.
From the UCI HAR 'features_info.txt' document:
-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 UCI HAR set also contains mean(), std() , and several other values for each of these parameters, labeled by appending '_mean()' or 'std()' to the end of the variable name. Only the mean() and std() parameters were used here.
The 'tidy_result.txt' document provided here uses the same naming convention as the UCI HAR study, but appends 'mean_' to the beginning of the variable name such that:
'tBodyAcc_mean_X' from the original set becomes 'mean_tBodyAcc_mean_X' in the summary.