Automatic assignment and fitting of spectra and the nearest lines plot is described in "Automatic and Semi-Automatic Assignment and Fitting of Spectra with PGOPHER". C. M. Western and B. E. Billinghurst, Physical Chemistry Chemical Physics. The automatic fitting is based on Autofit 1.0 developed in the lab of Brooks Pate at the University of Virginia, and further developed by developed by Steve Shipman, Ian Finneran New College of Florida - see http://faculty.virginia.edu/bpate-lab/autofit/intro.html and N. A. Seifert, I. A. Finneran, C. Perez, D. P. Zaleski, J. L. Neill, A. L. Steber, R. D. Suenram, A. Lesarri, S. T. Shipman, B. H. Pate, J Mol. Spectrosc. 312, 13, 2015. The PGOPHER implementation uses a similar logic, but written in a much more general way to allow use on a much wider range of molecule and spectrum types. It has the potential to be much faster as the search process is integrated with the main program, so there is a much reduced overhead with each test assignment. There is also a comprehensive set of interactive tools available, including the nearest lines plot that is unique to PGOPHER to make many different styles of assignment possible.
Note that the automatic fitting process has changed in version 10.1; if you are familiar with
the previous version, the advanced diagnostic tools section below is a suitable