Overlay NMR Spectra Using ggplot2

Overlay multiple NMR spectra in a specified chemical shift region using ggplot2. Faceting, coloring, and line types can be controlled via an annotation list. Useful for QC and visual inspection of subsets or trends in spectral data.

Usage

specOverlay(
  X,
  ppm,
  shift = c(0, 0.1),
  an = list("Group"),
  alp = 0.7,
  size = 0.5,
  title = "",
  ...
)

Arguments

X

Numeric matrix. NMR data with spectra in rows.

ppm

Numeric vector. Chemical shift values corresponding to columns of X.

shift

Numeric vector of length 2. Region in ppm to plot (recommended to be small for performance).

an

Named list of 1–3 elements for grouping: 1st for facetting, 2nd for color, 3rd for line type.

alp

Numeric. Alpha transparency of lines (0 to 1).

size

Numeric. Line width (e.g., 0.5).

title

Character. Plot title.

...

Additional arguments passed to facet_grid.

Value

A ggplot object.

Details

The first element in an defines the facet grouping and must always be specified. Additional elements define coloring and line type. Use short ppm ranges (e.g., 5.15–4.6) to improve performance.

Examples

data(covid)
X <- covid$X
ppm <- covid$ppm
an <- covid$an
specOverlay(X, ppm, shift = c(5.15, 4.6), an = list(Group = an$type))