ndvi_derivatives: Calculates derivatives of idealized NDVI

In sephora: Statistical Estimation of Phenological Parameters

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? degree=0 corresponds to harmonic regression fit
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

sephora documentation built on May 29, 2024, 4:57 a.m.