R/doubleDiff.R

In TIMP: Fitting Separable Nonlinear Models in Spectroscopy and Microscopy

doubleDiff <- function(dd, file = "doubleDiff.txt") {
  psi <- dd@psi.df
  psi[2:dd@nt, ] <- psi[2:dd@nt, ] - psi[1:(dd@nt - 1), ]
  dd@psi.df <- psi[-1, ]
  dd@x <- dd@x[-1]
  dd@nt <- length(dd@x)
  write.table(t(dd@psi.df),
    file = file,
    quote = FALSE, row.names = dd@x2,
    col.names = dd@x
  )
  dd
}