Apodisation function dispatcher

Generates apodisation (window) functions for FID processing. The function applies one of several predefined window shapes, selected via pars$fun.

Usage

.fidApodisationFct(n, pars)

Arguments

n

Integer. Number of data points.

pars

List of parameters defining the apodisation. Must contain element fun specifying the window type.

Value

Numeric vector of length n with apodisation weights.

Details

Supported apodisation functions and parameters:

"uniform"

No apodisation (all weights = 1).

"exponential"

Exponential decay window.

lb

Line broadening parameter.

"cosine"

Cosine window (no additional parameters).

"sine"

Sine window (no additional parameters).

"sem"

Sine-modulated exponential window.

lb

Exponential decay parameter.

"expGaus_resyG"

Exponential-Gaussian hybrid window.

lb

Exponential decay parameter.

gb

Gaussian broadening parameter.

aq_t

Acquisition time.

"gauss"

Gaussian window (Bruker-style).

lb

Line broadening parameter.

gb

Gaussian broadening factor.

para

List containing acquisition parameters (e.g. a_SW_h, a_TD).

Examples

# Internal FID apidisation functions (illustrative only)
f_apod <- c("sine","cosine","exponential","sem")

# create toy fid
n <- 200; t <- seq(0,1,len=n)
fid <- exp(-5*t)*cos(20*pi*t)

# generate & apply apodisation windows
A  <- sapply(f_apod, \(f) metabom8:::.fidApodisationFct(n, list(fun=f, lb=-0.2)))
Fp <- sweep(A, 1, fid, `*`)

# generate spectra
S  <- apply(Fp, 2, \(x) Mod(fft(x))[1:(n/2)])

# graphhics
cols <- 1:ncol(A)

par(mfrow=c(2,2), mar=c(3,3,2,1))
plot(t, fid, type="l", lwd=2, main="FID")
matplot(t, A, type="l", lwd=2, col=cols, main="Windows")
matplot(t, Fp, type="l", lwd=2, col=cols, main="Windowed FID")
matplot(S, type="l", lwd=2, col=cols, main="Spectrum")

legend("topright", f_apod, col=cols, lty=1, bty="n", cex=.8)