| ndvi_derivatives {sephora} | R Documentation |
Calculates derivatives of idealized NDVI
Description
Provides function expression of derivatives of an idealized NDVI curve fitted through a harmonic regression model
Usage
ndvi_derivatives(amp, pha, degree, L)
Arguments
amp |
numeric vector specifying amplitude parameter |
pha |
numeric vector specifying phase angle parameter |
degree |
integer. What derivative's degree should be calculated?
|
L |
integer giving the number of observations per period |
Details
This function returns the derivatives of f(t), with respect
to t, when f has the representation:
f(t) = \sum_{k=1}^{p} a[i] cos( (2 \pi k t)/L - \phi[i] ),
where a and \phi are substituted by the vectors amp
and phase, respectively. The degree of the derivative is given by the
argument degree.
Value
A function expression
Note
For historic reasons, we ended up using the name ndvi_derivatives
for this function, but it can be used to calculate derivatives of any function
expression defined through amp, pha, degree and L.
See Also
phenopar, phenopar_polygon, haRmonics