Notice:
This code is provided as it is, there might be errors,may not work sometimes, so use it with your discretion. If encounter any problem, please first read the description below, and then the two references.

[parmin,resnom,res,exitflag]= fit2voigt(dat,par0)
This code do the following: if you supply a two column spectral data ( first column is wavenumber, second column is absorbance) dat, and initial peak parameters par0, it gives you optimised voigt line shape parameters parmin, and the fit and fitting quality information.
It uses the the Voigt/complex error function (File ID: #47801) of Sanjar Abrarov. You need to download the code, and put under the same folder as these files.
Analytical jacobians is included.
Also included is the test data. you can test by running the voigtfit_test m.file

References:
R.J. Wells, Rapid approximation to the Voigt/Faddeeva function and its derivatives, JQSRT 62(1999), 29-48
S. M. Abrarov and B. M. Quine, Appl. Math. Comput., 218 (2011) 1894-1902