Calculates the spectral derivative at a specific wavelength using one of three methods:
"central": Central difference method, f'(x) ≈ f(x+h1) - f(x-h2)/(h1+h2)
"forward": Forward difference method, f'(x) ≈ f(x+h) - f(x)/h
"backward": Backward difference method, f'(x) ≈ f(x) - f(x-h)/h
Where h, h1, and h2 are wavelength differences between bands. The derivative provides information about the rate of change in reflectance, which can be useful for identifying absorption features and inflection points.
Usage
calculate_derivative(
raster,
derivative_name,
band,
method = "central",
extent = NULL,
extension = NULL,
filename = NULL
)Arguments
- raster
terra SpatRaster of normalized capture data.
- derivative_name
a character, lower case name of calculated derivative.
- band
numeric, wavelength at which to calculate the derivative.
- method
character, method to use for derivative calculation. One of "central" (default), "forward", or "backward".
- extent
an extent or SpatVector used to subset SpatRaster. Defaults to the entire SpatRaster.
- extension
character, a graphic format extension.
- filename
NULL (default) to write automatically into products, provide full path and extension to override.
See also
Other Spectral calculations:
calculate_band_difference(),
calculate_band_ratio(),
calculate_lambdaremp(),
calculate_ndi(),
calculate_raba(),
calculate_rabd(),
calculate_rmean()