  In the package corr2D two-dimensional correlation analysis is implemented in
R. This paper describes how two-dimensional correlation analysis is done in the
package and how the mathematical equations are translated into R code. The
paper features a simple tutorial with executable code for beginners, insight
into at the calculations done before the correlation analysis, a detailed look
at the parallelization of the fast Fourier transformation based correlation
analysis and a speed test of the calculation. The package corr2D offers the
possibility to preprocess, correlate and postprocess spectroscopic data using
exclusively the R language. Thus, corr2D is a welcome addition to the toolbox
of spectroscopists and makes two-dimensional correlation analysis more
accessible and transparent.
