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Help njerk
Compute Norm Jerk
Syntax
j = njerk(A,fs) % Matlab & Octave j <- njerk(A, fs) #R
Description
Compute the norm-jerk from triaxial acceleration data. The norm-jerk is ||dA/dt||, where ||x|| is the 2-norm of x, i.e., the square-root of the sum of the squares of each axis.
Inputs
| Input var | Description | Units | Default value |
|---|---|---|---|
| A | is a nx3 acceleration matrix with columns [ax ay az]. Acceleration can be in any consistent unit, e.g., g or m/s2. | g or m/s2 | N/A |
| fs | is the sampling rate in Hz of the acceleration signals. This is used to estimate the differential by a first-order difference. | N/A | N/A |
Outputs
| Output var | Description | Units |
|---|---|---|
| j | is a column vector with the same number of rows as in A. If the unit of A is m/s2, the norm-jerk has unit m/s3. If the unit of A is g, the norm-jerk has unit g/s. As j is the norm of the jerk, it is always positive or zero (if the acceleration is constant). The final value in j is always 0 because the last finite difference cannot be calculated. | m/s3 or g/s |
Notes & assumptions
- A can be in any frame as the norm-jerk is rotation independent. A must have at least 2 rows (i.e., n>=2)
- As j is the norm of the jerk, it is always positive or zero (if the acceleration is constant). The final value in j is always 0 because the last finite difference cannot be calculated.
Example
Matlab & Octave
j = njerk([1,2,3;2,2,4;1,-2,4;4,4,4],5) j = [7.0711;20.6155;33.541;0]
R
sampleMatrix = matrix(c(1, 2, 3, 2, 2, 4, 1, -2, 4, 4, 4, 4), byrow = TRUE, nrow = 4, ncol = 3) j <- njerk(A=sampleMatrix, fs=5) j <- c(7.0711, 20.6155, 33.541, 0)
About
bugs@animaltags.org Last modified: 15 August 2012