Table 1.
Description of features extracted from the raw data.
| Feature | Description | |
| Time | ||
|
|
Mean of vector magnitude | Sample mean of the VMa in the window |
|
|
SD of vector magnitude | SD of VM in the window |
|
|
Mean angle of acceleration relative to vertical on the deice | Sample mean of the angle between x-axis and VM in the window |
|
|
SD of the angle of acceleration relative to vertical on the device | Sample SD of the angles in the window |
|
|
Covariance | Covariance of the VM in the window |
|
|
Skewness | Skewness of the VM in the window |
|
|
Kurtosis | Kurtosis of the VM in the window |
|
|
Entropy | Entropy of the VM in the window |
|
|
Coefficient of variation | SD of VM in the window divided by the mean, multiplied by 100 |
|
|
Corr(x,y) | Correlation between x-axis and y-axis |
|
|
Corr(y,z) | Correlation between y-axis and z-axis |
|
|
Corr(x,z) | Correlation between x-axis and z-axis |
| Frequency | ||
|
|
Percentage of the power of the VM that is in 0.6-2.5 Hz | Sum of moduli corresponding to frequency in this range divided by sum of moduli of all frequencies |
|
|
Dominant frequency of VM | Frequency corresponding to the largest modulus |
|
|
Fraction of power in VM at dominant frequency | Modulus of the dominant frequency or sum of moduli at each frequency |
aVM: vector magnitude.