R: Calculation of warping coefficients when applying more than...

calc.multicoef {ptw} | R Documentation

## Calculation of warping coefficients when applying more than one warping function successively

### Description

Applying two (or more) warping function after each other can be described with one warping function of a higher warping degree. This function provides the coefficients of this higher degree warping function.

### Usage

    calc.multicoef(coef1, coef2)

### Arguments

`coef1` | vector containing the warping coefficients of the first applied warping function
`coef2` | vector containing the warping coefficients of the second applied warping function

### Details

This function uses Pascal's simplex to calculate the new warping coefficients.

When applying three warping functions successively (first a, then b and finally c - here a, b and c are vectors of warping coefficients), first calculate the new coefficients for b and c, and afterwards the coefficients for a with these new coefficients. So the coefficients for the total warping function can be calculated via `calc.multicoef(a, calc.multicoef(b, c))`.

### Value

a vector containing the corrected warping coefficients

### Author(s)

Jan Gerretzen

### References

Bloemberg, T.G., et al. (2010) "Improved parametric time warping for Proteomics", Chemometrics and Intelligent Laboratory Systems, 104 (1), 65 – 74.

### See Also

`calc.zerocoef`

### Examples

    data(gaschrom)
    ref <- gaschrom[1,]
    samp <- gaschrom[16,]
    coef1 <- c(100,1.1, 1e-5)
    coef2 <- c(25, 0.95, 3.2e-5)
    gaschrom.ptw <- ptw(ref, samp, init.coef = coef1, try = TRUE)
    ref.w <- gaschrom.ptw$reference
    samp.w <- gaschrom.ptw$warped.sample
    samp.w[is.na(samp.w)] <- 0
    gaschrom.ptw2 <- ptw(ref.w, samp.w, init.coef = coef2, try = TRUE)
    plot(c(gaschrom.ptw2$warped.sample), type = "l")

    corr.coef <- calc.multicoef(coef1, coef2)
    gaschrom.ptw3 <- ptw(ref, samp, init.coef = corr.coef, try = TRUE)
    lines(c(gaschrom.ptw3$warped.sample), col = 2, lty = 2)

[Package ptw version 1.9-12 Index]