R/compOsc.R

In TIMP: Fitting Separable Nonlinear Models in Spectroscopy and Microscopy

"compOsc" <-
  function(irfpar, x, oscspec, oscpar) {
    type <- oscspec$type
    cohcols <- vector()
    if (tolower(type) == "harmonic") {
      if ((length(oscpar) > 0)) {
        if ((length(oscpar) >= 3)) {
          if ((length(oscpar) %% 3) != 0) {
            warning(sprintf("oscpar is not a multiple of 3"))
          }
          ncolosc <- floor(length(oscpar) / 3)
          cohcols <- matrix(0, nrow = length(x), ncol = ncolosc)
          for (i in 1:ncolosc) {
            t0 <- irfpar[1]
            tt <- x - t0
            ts <- oscpar[1 + (i - 1) * 3] # timeshift
            g <- oscpar[2 + (i - 1) * 3] # g or gamma (damping)
            w0 <- oscpar[3 + (i - 1) * 3] # w0 or omega_0 (frequency)
            heavyside <- rep(1, length(tt))
            heavyside[which(tt < 0)] <- 0
            cohcols[, i] <- heavyside * Re(
              (-exp(tt * (-g - sqrt(as.complex(g^2 - w0^2)))) +
                exp(tt * (-g + sqrt(as.complex(g^2 - w0^2)))))
              / (2 * sqrt(as.complex(g^2 - w0^2)))
            )
          }
        }
      } else {
        warning(sprintf("oscspec$type is %s but oscpar is empty", type))
      }
    }
    cohcols[is.na(cohcols)] <- 0
    cohcols
  }