wl2i {hyperSpec} | R Documentation |
wl2i
returns the column indices for the spectra matrix for the
given wavelengths.
i2wl
converts column indices into wavelengths.
wl2i(x, wavelength = stop ("wavelengths are required.")) i2wl(x, i)
x |
a hyperSpec object |
wavelength |
the wavelengths to be converted into column indices, either numeric or a formula, see details. |
i |
the column indices into the spectra matrix for which the wavelength is to be computed |
If wavelength
is numeric, each of its elements is converted to the respective index.
Values outside the range of x@wavelength
become NA
.
If the range is given as a formula (i.e. start ~ end
, a sequence
index corresponding to start : index corresponding to end
is returned. If the wavelengths are not ordered, that may lead to chaos. In this case, call
orderwl
first.
Two special variables can be used: min
and max
, corresponding to the lowest and highest
wavelength of x
, respectively.
start and end may be complex numbers. The resulting index for a complex x is then
index (Re (x)) + Im (x)
A numeric containing the resulting indices and wavelengths, respectively.
C. Beleites
flu wl2i (flu, 405 : 407) wl2i (flu, 405 ~ 407) ## beginning of the spectrum to 407 nm wl2i (flu, min ~ 407) ## 2 data points from the beginning of the spectrum to 407 nm wl2i (flu, min + 2i ~ 407) ## the first 3 data points wl2i (flu, min ~ min + 2i) ## from 490 nm to end of the spectrum wl2i (flu, 490 ~ max) ## the last 8 data points wl2i (flu, max - 7i ~ max) ## get 450 nm +- 3 data points wl2i (flu, 450 - 3i ~ 450 + 3i) wl2i (flu, 300 : 400) ## all NA: wl2i (flu, 600 ~ 700) ## NULL: completely outside flu's wavelength range i2wl (chondro, 17:20)