R/ir_get_spectrum.R

In ir: Functions to Handle and Preprocess Infrared Spectra

#' Extracts selected spectra from an object of class `ir`
#'
#' `ir_get_spectrum` extracts selected spectra from an object of class `ir`.
#'
#' @param x An object of class [`ir`][ir_new_ir()].
#'
#' @param what A numeric vector with each element representing a row in `x`
#' for which to extract the spectrum.
#'
#' @return An integer vector with the same length as `wavenumber` with the
#' row indices of `x` corresponding to the wavenumber values in `wavenumber`.
#'
#' @examples
#' x <-
#'    ir::ir_sample_data %>%
#'    ir::ir_get_spectrum(what = c(5, 9))
#'
#' @export
ir_get_spectrum <- function(x,
                            what) {

  # checks
  ir_check_ir(x)
  if(!(is.numeric(what))){
    rlang::abort("`what` must be numeric.")
  }
  what_integer <- what %% 1 == 0
  if(!all(what_integer)) {
    if(sum(!what_integer) == 1) {
      rlang::abort(paste0("`what` must only contain whole numbers. Element ", which(!what_integer), " is a double."))
    } else {
      rlang::abort(paste0("`what` must only contain whole numbers. Elements ", which(!what_integer), " are doubles."))
    }
  }

  x$spectra[what]

}