R: 16 calibration GC traces

gaschrom {ptw} | R Documentation

## 16 calibration GC traces

### Description

The object `gaschrom` contains 16 calibration GC traces, measured at 5,000 time points. A peak-picked version is available as object `gaschrom.st` (see example).

### Usage

    data(gaschrom)

### Source

Claire Boucon, Unilever

### References

Eilers, P.H.C. (2004) "Parametric Time Warping", Analytical Chemistry, 76 (2), 404 – 411.

### Examples

    data(gaschrom)

    ## the gaschrom.st object has been generated in the following way:
    ## Not run:
    pick.peaks <- function(x, span) {
      span.width <- span * 2 + 1
      loc.max <- span.width + 1 -
          apply(embed(x, span.width), 1, which.max)
      loc.max[loc.max == 1 | loc.max == span.width] <- NA

      pks <- loc.max + 0:(length(loc.max)-1)
      pks <- pks[!is.na(pks)]
      pks.tab <- table(pks)

      pks.id <- as.numeric(names(pks.tab)[pks.tab > span])

      cbind(rt = pks.id, I = x[pks.id])
    }

    gaschrom <- t(apply(gaschrom, 1, baseline.corr))
    gaschrom.st <- lapply(1:nrow(gaschrom),
                          function(ii)
                          pick.peaks(gaschrom[ii,], span = 11))
    ## remove peaks with an intensity below 10
    gaschrom.st <- lapply(gaschrom.st,
                          function(pk)
                          pk[pk[,2] >= 10,])

    ## End(Not run)
    plot(gaschrom[1,], type = "l", xlim = c(3000, 3500), ylim = c(0, 200))
    abline(h = 10, lty = 2, col = 2)
    abline(v = gaschrom.st[[1]], col = 4)

[Package ptw version 1.9-12 Index]