ChemoSpec (version 3.0-1)

findTMS: Find the TMS/TSP Peak in an NMR Spectrum.

Description

This is a simple function to find the TMS or TSP peak in proton NMR spectrum. It simply finds the rightmost large peak in the spectrum.

Usage

findTMS(x, span, sn, thresh = 0.2, debug = FALSE)

Arguments

x

Vector of intensities of the spectrum. The frequency aspect is handled simply as the index along the intensity vector.

span

Integer; the number of data points to use as a window on either side of a peak when calculating the SN. See the code for exactly how this window is created. Larger values find fewer peaks.

sn

Numeric; the minimum value of the signal-to-noise ratio for detecting a peak.

thresh

Numeric; a value in 0...1 which gives the quantile of peaks in the entire spectrum which should be kept on the short list for finding the TMS peak.

debug

Logical; if TRUE write progress and findings to screen.

Value

• The index of the peak believed to be the TMS peak.

Details

The rightmost peak is sought, so the spectrum must be presented in the usual high ppm --> low ppm format. Calls calcSN which will issue warnings when peaks are near the edges of the spectrum.

References

https://github.com/bryanhanson/ChemoSpec

Examples

# Some test data:
set.seed(99)
vec <- abs(rnorm(100))
vec[12] <- 10
vec[75] <- 31 # create two larger peaks

ans <- findTMS(vec, 20, 5)
ans # index as set above (75)
plot(vec, type = "l")
abline(v = ans, col = "red")