does anyone have code for fitting a mixed exponential distribution?

Not sure if I totally understand the request but if you are looking for nonlinear regression tools "nonlin" is a good application to use.
http://archives.math.utk.edu/software/msdos/statistics/nonlin25/.html

The application is pretty old and runs in dos mode using a text file (with a .nlr extension) to contain the data and the problem definition.

to use I would copy one of the example .nlr files, open in a text editor and then change the parameters and equations to suit. The input data can be copied and pasted directly into the file from excel.

to run you can either enter the directory in the dos shell and type the following:-

nonlin datafit

(where your problem definition and data file is contained in a file called "datafit.nlr"

The results should appear in "datafit.lst"... but if they are displayed on the screen you should be able to pipe them to file by using the command

nonlin datafit > datafit.lst


or you can create a batch file and run it from there (see "demo.bat"<br><br>Post edited by: DaveCwork, at: 2007/04/18 14:06

Dave, thanks for the response.

To give you more info, I have a data set that has an exponential distribution. I want to fit a mixed exponential equation to it. I can do this in other packages, but these packages are not widely available outside of the research area for a variety of reasons, including cost. However, excel is widely available. While fitting such curves to this data might be more "clumsy" in excel, I believe it's doable and would facilitate the use of research that relies upon the use of the exponential distribution parameters.

I am not sure quite what you are after but will XlXtrFun™ Extra Functions for Microsoft Excel be any use to you?

Many thanks BillyNoMates - have downloaded and will have a look at it.