hsdar (version 0.4.1)

derivative.speclib: Derivation

Description

Calculate derivations of spectra

Usage

derivative.speclib(x, m = 1, method = "sgolay", ...)

Arguments

x

Object of class Speclib.

m

Return the m-th derivative of the spectra.

method

Character string giving the method to be used. Valid options are "finApprox" or "sgolay".

...

Further arguments passed to sgolayfilt.

Value

• Object of class Speclib.

Details

Two different methods are available:

• Finite approximation (finApprox):

{ $$\frac{dr}{d\lambda}=\frac{r(\lambda_i)-r(\lambda_{i+1})}{\Delta\lambda},$$ where $r_i$ is the reflection in band $i$ and $\Delta\lambda$ the spectral difference between adjacent bands.} Savitzky-Golay derivative computation (sgolay){ }

References

Tsai, F. & Philpot, W. (1998): Derivative analysis of hyperspectral data. Remote Sensing of Environment 66/1. 41-51.

See Also

sgolayfilt, vegindex

Examples

data(spectral_data)

## Calculate 1st derivation
d1 <- derivative.speclib(spectral_data)

## Calculate 2nd derivation
d2 <- derivative.speclib(spectral_data, m = 2)

## Calculate 3rd derivation
d3 <- derivative.speclib(spectral_data, m = 3)

par(mfrow=c(2,2))
plot(spectral_data)
plot(d1)
plot(d2)
plot(d3)