This was preparred with the aid of README.txt and features_info.txt, which are files found in the folder "UCI HAR Dataset", which appears in your working directory after running run_analysis.R.
Here is a link to the data set home page: Human Activity Recognition Using Smartphones Data Set
SubjectID is a number between 1 and 30, each representing one of the thirty participants in the study.
ActivityID is one of the six different activites that were used to generate data:
- laying
- sitting
- standing
- walking
- walkingdownstairs (walking down stairs)
- walkingupstairs (walking up stairs)
The remaining 66 columns have descriptive variable names that follow the following naming conventions:
- a prefix "t" represents "time"
- a prefix "f" represents "frequency domain signal"
- a substring "BodyAcc" represents (estimated) body acceleration
- a substring "GravityAcc" represents (total) gravity acceleration
- a substring "Gyro" represents angular velocity measured by the gyroscope
- a substring "Mag" represents magnitude
- a substring "Jerk" represents the acceleration of the acceleration
- a substring "Mean" represents that it is a mean
- a substring "StdDev" represents that it is a standard deviation
- a suffix "X", "Y", or "Z" represents motion in those respective directions
The original values of these variables were normalized and bounded within [-1,1]. After running run_analysis.R, the values that appear in tidydata.txt are: the mean of that variable given each combination of Subject and Activity. Note that the resulting values will still be within the interval [-1,1]. There are 30 subjects and 6 activiies, leading to 180 combinations of subject and activity. For each of those 180 combinations, all values of a given variable associated with the given combination where averaged.
For example, row 3 represents Subject 3 doing the activity Laying. Column 3 is "tBodyAccMeanX". Then, the value in row 3, column 3 is then the mean of all the values of Subject 3's average body acceleration in the X direction while laying down.
| Column Number | Variable Name | Description |
|---|---|---|
| 1 | SubjectID | Subject ID |
| 2 | ActivityID | Activity ID |
| 3 | tBodyAccMeanX | Average body acceleration in X direction |
| 4 | tBodyAccMeanY | Average body acceleration in Y direction |
| 5 | tBodyAccMeanZ | Average body acceleration in Z direction |
| 6 | tBodyAccStdDevX | Standard deviation of body acceleration in X direction |
| 7 | tBodyAccStdDevY | Standard deviation of body acceleration in Y direction |
| 8 | tBodyAccStdDevZ | Standard deviation of body acceleration in Z direction |
| 9 | tGravityAccMeanX | Average gravity acceleration in X direction |
| 10 | tGravityAccMeanY | Average gravity acceleration in Y direction |
| 11 | tGravityAccMeanZ | Average gravity acceleration in Z direction |
| 12 | tGravityAccStdDevX | Standard deviation of gravity acceleration in X direction |
| 13 | tGravityAccStdDevY | Standard deviation of gravity acceleration in Y direction |
| 14 | tGravityAccStdDevZ | Standard deviation of gravity acceleration in Z direction |
| 15 | tBodyAccJerkMeanX | Average body jerk in X direction |
| 16 | tBodyAccJerkMeanY | Average body jerk in Y direction |
| 17 | tBodyAccJerkMeanZ | Average body jerk in Z direction |
| 18 | tBodyAccJerkStdDevX | Standard deviation of body jerk in X direction |
| 19 | tBodyAccJerkStdDevY | Standard deviation of body jerk in Y direction |
| 20 | tBodyAccJerkStdDevZ | Standard deviation of body jerk in Z direction |
| 21 | tBodyGyroMeanX | Average body rotation in X direction |
| 22 | tBodyGyroMeanY | Average body rotation in Y direction |
| 23 | tBodyGyroMeanZ | Average body rotation in Z direction |
| 24 | tBodyGyroStdDevX | Standard deviation of body rotation in X direction |
| 25 | tBodyGyroStdDevY | Standard deviation of body rotation in Y direction |
| 26 | tBodyGyroStdDevZ | Standard deviation of body rotation in Z direction |
| 27 | tBodyGyroJerkMeanX | Average body rotation jerk in X direction |
| 28 | tBodyGyroJerkMeanY | Average body rotation jerk in Y direction |
| 29 | tBodyGyroJerkMeanZ | Average body rotation jerk in Z direction |
| 30 | tBodyGyroJerkStdDevX | Standard deviation of body rotation jerk in X direction |
| 31 | tBodyGyroJerkStdDevY | Standard deviation of body rotation jerk in Y direction |
| 32 | tBodyGyroJerkStdDevZ | Standard deviation of body rotation jerk in Z direction |
| 33 | tBodyAccMagMean | Average magnitude of body acceleration |
| 34 | tBodyAccMagStdDev | Standard deviation of magnitude of body acceleration |
| 35 | tGravityAccMagMean | Average magnitude of gravity acceleration |
| 36 | tGravityAccMagStdDev | Standard deviation of magnitude of gravity acceleration |
| 37 | tBodyAccJerkMagMean | Average magnitude of body jerk |
| 38 | tBodyAccJerkMagStdDev | Standard deviatiion of magnitude of body jerk |
| 39 | tBodyGyroMagMean | Average magnitude of body rotation |
| 40 | tBodyGyroMagStdDev | Standard deviation of magnitude of body rotation |
| 41 | tBodyGyroJerkMagMean | Average magnitude of body rotation jerk |
| 42 | tBodyGyroJerkMagStdDev | Standard deviation of magnitude of body rotation jerk |
| 43 | fBodyAccMeanX | Average body acceleration in X direction |
| 44 | fBodyAccMeanY | Average body acceleration in Y direction |
| 45 | fBodyAccMeanZ | Average body acceleration in Z direction |
| 46 | fBodyAccStdDevX | Standard deviation of body acceleration in X direction |
| 47 | fBodyAccStdDevY | Standard deviation of body acceleration in Y direction |
| 48 | fBodyAccStdDevZ | Standard deviation of body acceleration in Z direction |
| 49 | fBodyAccJerkMeanX | Average body jerk in X direction |
| 50 | fBodyAccJerkMeanY | Average body jerk in Y direction |
| 51 | fBodyAccJerkMeanZ | Average body jerk in Z direction |
| 52 | fBodyAccJerkStdDevX | Standard deviation of body jerk in X direction |
| 53 | fBodyAccJerkStdDevY | Standard deviation of body jerk in Y direction |
| 54 | fBodyAccJerkStdDevZ | Standard deviation of body jerk in Z direction |
| 55 | fBodyGyroMeanX | Average body rotation in X direction |
| 56 | fBodyGyroMeanY | Average body rotation in Y direction |
| 57 | fBodyGyroMeanZ | Average body rotation in Z direction |
| 58 | fBodyGyroStdDevX | Standard deviation of body rotation in X direction |
| 59 | fBodyGyroStdDevY | Standard deviation of body rotation in Y direction |
| 60 | fBodyGyroStdDevZ | Standard deviation of body rotation in Z direction |
| 61 | fBodyAccMagMean | Average body rotation magnitude |
| 62 | fBodyAccMagStdDev | Standard deviation of body rotation magnitude |
| 63 | fBodyBodyAccJerkMagMean | Average magnitude of body jerk |
| 64 | fBodyBodyAccJerkMagStdDev | Standard deviation of magnitude of body jerk |
| 65 | fBodyBodyGyroMagMean | Average magnitude of body rotation |
| 66 | fBodyBodyGyroMagStdDev | Standard deviation of magnitude of body rotation |
| 67 | fBodyBodyGyroJerkMagMean | Average magnitude of body rotation jerk |
| 68 | fBodyBodyGyroJerkMagStdDev | Standard deviation of body rotation jerk |