This function returns a normalized difference index value for an arbitrary pair of wavebands.
normalized_diff_ind(spct, plus.w.band, minus.w.band, f, ...)
an R object
waveband objects The waveband determine the region of the spectrum used in the calculations
waveband objects The waveband determine the region of the spectrum used in the calculations
function used for integration taking spct as first argument and a list of wavebands as second argument.
additional arguments passed to f
A numeric value for the index