Subject: Summary on deconvoluting software

From: [email-masked] (Hr Dr. S. Shapiro)
Date: Mon, 12 Aug 1996 08:25:12 +0200 (MEST)

Dear Colleagues;

     A few days ago I posted a query about PC programmes than can be used for
deconvoluting spectra or chromatogrammes.  Despite the season a number of useful
replies were forthcoming, which I wish to summarise for the list.

     One respondent advised me of a programme written in FORTRAN77 named LGFIT2,
which will deconvolute complex spectra into sets of overlapping Lorentzian or
Gaussian bands, and which is downloadable from http:// www.kfa-juelich.de:80/
zam/CompServ/software/mathe/mathsrc/cpc/abmk.cpc; unfortunately, at the moment
I myself can't download from the WWW.  Moreover, I have neither the tools nor
the skills to port a FORTRAN77 programme to DOS/Windows.  However, if anybody
out there would be willing to undertake such a challenging port and actually    port and g port and actually suc-
succeeds, I would very much like to hear from you later.                        r from you [3~ceeds, I would very much like to hear from you later.

     Another kind correspondent pointed out that the principle of superposition
says that a chromatogramme or spectrum consisting of two overlapping peaks can
be expressed as

            f(x) = A*exp((-a)*(x-xa)**2)) + B*exp((-b)*(x-xb)**2))

so it is "simply" a matter of calculating appropriate values for A, a, xa, B, b,
and xb that will regenerate your spectrum or chromatogramme of interest.  He
added that it shouldn't be such a formidible task to do this by hand (well, I
suppose not if you've hand a brain implant from Riemann) but that it can also be
done rather simply using Excel or some similar spreadsheet programme.  Again,
unfortunately, I don't have ready access to Excel or related spreadsheet pro-
grammes, and a couple of "quickie" attempts to arrive at the six parameters by
hand weren't very fruitful.

     Finally, I did a WWW (Lycos) search for "curve fitting" and located a Win-
dows shareware programme by Prof. Dr. Daniel Hyams of Clemson University that
did the trick.  Since the sum of two Gaussians is not included in the pro-
gramme's repertoire of mathematical models, I simply added the aforementioned
equation to "User's Models" and ran my data through it on a Pentium-90 MHz fit-
ted with MS-DOS 6.2 + Windows for Workgroups 3.11 + 80 MB RAM.  A minute or two
after initiating the calculation out popped a set of six parameters which gene-
rated a curve mathing my experimental one with a correlation coefficient
r = 0.9999, which I think you will agree is reasonably acceptable.

     Since Prof. Dr. Hyams' programme is shareware (registration fee = US$35.-),
I hesitate to provide the FTP site from which I downloaded it.  For details, I
suggest that you contact Prof. Dr. Hyams personally at

                        [email-masked].

With kindest regards,

S. Shapiro
ZH
[email-masked]