# derivative_speclib: Derivation

### Description

Calculate derivations of spectra

### Usage

 1 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.

### Details

Two different methods are available:

• Finite approximation (finApprox):

\frac{dr}{dλ}=\frac{r(λ_i)-r(λ_{i+1})}{Δλ},

where r_i is the reflection in band i and Δλ the spectral difference between adjacent bands.

• Savitzky-Golay derivative computation (sgolay)

### Value

Object of class Speclib.

Lukas Lehnert

### References

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

sgolayfilt, vegindex

### Examples

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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) 

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