CodeBook.Rmd

---
title: "CodeBook"
author: "Alberto Algarra Alarcon"
date: "Sunday, June 21, 2015"
output: html_document
---
The "run_analysis.R" script run a series of commands in order to create a tidy data frame from two separate datasets: the training and test dataset of a wearable computing app tested in a Samsung Galaxy SII.

For the script to work, the working directory should be the one containing the smartphone's data folder (UCI HAR Dataset). 

Each row represents the **_CALCULATED MEAN_** of the measurements taken from each person and activity. Each column represents a different variable, the first two are categorical and define the subject and the activity measured:

1. **_Subject_**: a number with each volunteer person who participated in the study.
2. **_Activity_**: name of the activity carried out by the subject. There are six. levels: walking, walking upstairs, walking downstairs, sitting, standing and lying.

The rest of the variables are subtracted from the available variables. These numerical variables represent the **mean** and the **standard deviation** of the signals obtained either by the phone's **accelerometer** (measured in _linear acceleration_) or **gyroscope** (measured in _angular velocity_), which are represented as "Acc" and "Gyro" in the variable's names, respectively. The prefix **"t"** denotes that the measurements were taken at a constant rate of 50 Hz. The prefix **"f"** indicates that a Fast Fourier Transformation was applied to some of the signals.
The accelerometer's signal have gravitational and body motion components, there the **"body"** and **"gravity"** in the name of each variable. Body linear acceleration and angular velocity were derived in time to obtain **Jerk** signals. Also the magnitude (**Mag**) of these three-dimensional signals were calculated using the Euclidean norm.
Each signal ad a directional component, denoted by the **X**, **Y** or **Z** direction.
These numerical variables are:

3. **_tBodyAcc-mean()-X_**
4. **_tBodyAcc-mean()-Y_**
5. **_tBodyAcc-mean()-Z_**
6. **_tBodyAcc-std()-X_**
7. **_tBodyAcc-std()-Y_**
8. **_tBodyAcc-std()-Z_**
9. **_tGravityAcc-mean()-X_**
10. **_tGravityAcc-mean()-Y_**
11. **_tGravityAcc-mean()-Z_**
12. **_tGravityAcc-std()-X_**
13. **_tGravityAcc-std()-Y_**
14. **_tGravityAcc-std()-Z_**
15. **_tBodyAccJerk-mean()-X_**
16. **_tBodyAccJerk-mean()-Y_**
17. **_tBodyAccJerk-mean()-Z_**
18. **_tBodyAccJerk-std()-X_**
19. **_tBodyAccJerk-std()-Y_**
20. **_tBodyAccJerk-std()-Z_**
21. **_tBodyGyro-mean()-X_**
22. **_tBodyGyro-mean()-Y_**
23. **_tBodyGyro-mean()-Z_**
24. **_tBodyGyro-std()-X_**
25. **_tBodyGyro-std()-Y_**
26. **_tBodyGyro-std()-Z_**
27. **_tBodyGyroJerk-mean()-X_**
28. **_tBodyGyroJerk-mean()-Y_**
29. **_tBodyGyroJerk-mean()-Z_**
30. **_tBodyGyroJerk-std()-X_**
31. **_tBodyGyroJerk-std()-Y_**
32. **_tBodyGyroJerk-std()-Z_**
33. **_tBodyAccMag-mean()_**
34. **_tBodyAccMag-std()_**
35. **_tGravityAccMag-mean()_**
36. **_tGravityAccMag-std()_**
37. **_tBodyAccJerkMag-mean()_**
38. **_tBodyAccJerkMag-std()_**
39. **_tBodyGyroMag-mean()_**
40. **_tBodyGyroMag-std()_**
41. **_tBodyGyroJerkMag-mean()_**
42. **_tBodyGyroJerkMag-std()_**
43. **_fBodyAcc-mean()-X_**
44. **_fBodyAcc-mean()-Y_**
45. **_fBodyAcc-mean()-Z_**
46. **_fBodyAcc-std()-X_**
47. **_fBodyAcc-std()-Y_**
48. **_fBodyAcc-std()-Z_**
49. **_fBodyAcc-meanFreq()-X_**
50. **_fBodyAcc-meanFreq()-Y_**
51. **_fBodyAcc-meanFreq()-Z_**
52. **_fBodyAccJerk-mean()-X_**
53. **_fBodyAccJerk-mean()-Y_**
54. **_fBodyAccJerk-mean()-Z_**
55. **_fBodyAccJerk-std()-X_**
56. **_fBodyAccJerk-std()-Y_**
57. **_fBodyAccJerk-std()-Z_**
58. **_fBodyAccJerk-meanFreq()-X_**
59. **_fBodyAccJerk-meanFreq()-Y_**
60. **_fBodyAccJerk-meanFreq()-Z_**
61. **_fBodyGyro-mean()-X_**
62. **_fBodyGyro-mean()-Y_**
63. **_fBodyGyro-mean()-Z_**
64. **_fBodyGyro-std()-X_**
65. **_fBodyGyro-std()-Y_**
66. **_fBodyGyro-std()-Z_**
67. **_fBodyGyro-meanFreq()-X_**
68. **_fBodyGyro-meanFreq()-Y_**
69. **_fBodyGyro-meanFreq()-Z_**
70. **_fBodyAccMag-mean()_**
71. **_fBodyAccMag-std()_**
72. **_fBodyAccMag-meanFreq()_**
73. **_fBodyBodyAccJerkMag-mean()_**
74. **_fBodyBodyAccJerkMag-std()_**
75. **_fBodyBodyAccJerkMag-meanFreq()_**
76. **_fBodyBodyGyroMag-mean()_**
77. **_fBodyBodyGyroMag-std()_**
78. **_fBodyBodyGyroMag-meanFreq()_**
79. **_fBodyBodyGyroJerkMag-mean()_**
80. **_fBodyBodyGyroJerkMag-std()_**
81. **_fBodyBodyGyroJerkMag-meanFreq()_**