Automate curve fitting

johnweeks wrote:

If you already have something that will load and graph the files, you might want to look at the Batch Curve Fitting package. See Analysis->Packages->Batch Curve Fitting. There is a demo experiment to introduce you to it as well: File->Example Experiments->Curve Fitting->Batch Curve Fit Demo. I believe it has a mode to use each fit as the initial guess for the next.

elliottmclean wrote:

I've got a procedure with a bespoke curve fitting function which I need to somehow make automatic for a number of files which need be loaded. At the moment the fitting function and the load/graph are in a seperate procedure files so my first question is as to whether that can be called from another procedure or whether I should combine it all into the one for simplicity?

For the first fit the fitting cursors need to be set to disregard noise at the end of the graph; and the initial guesses must be set to check as to whether the fit actually looks okay. Is it possible to call from a procedure to open the curve fitting dialog? Once the coefficients have been found for the first, they are fed into the function to fit the second, and then the coefficients from the second are used for the third and so on.

Any help on the matter would be greatly appreciated as I'm not sure where to even start.
Cheers.

wings wrote:

in each loop, get the wave from the name list and fit it using funcfit. in each loop the same coefficient wave is used, so you dont need to fill in initial guess, just as you want, the coefficients (fitting results of the last fitting) are automatically used in the next fitting.

elliottmclean wrote:

At the moment I've got a function that opens the select files to be analysed and retrieves the paths which is then passed as a global variable to other functions to either be graphed normally or as a waterfall plot. Is there an easier way to pass the waves between functions rather than passing a global variable of the paths and loading the files into each function? Would it be easier to load the waves into a data folder in a function and then access that data folder in each other function?

johnweeks wrote:

wings wrote:

in each loop, get the wave from the name list and fit it using funcfit. in each loop the same coefficient wave is used, so you dont need to fill in initial guess, just as you want, the coefficients (fitting results of the last fitting) are automatically used in the next fitting.

You need to be careful, though. If a fit fails, the contents of the coefficient wave may be garbage.
John Weeks
WaveMetrics, Inc.
support@wavemetrics.com

johnweeks wrote:

You really should avoid global variables like the plague unless you need them to store information that needs to persist from one invocation of your code to the next. The best way to work is to pass the waves via function WAVE parameters. Something like this:

Function loadAndAnalyse()
    LoadWave ...
    Wave w = $StringFromList(0, S_WaveNames)    // assumes you only ever load one wave, but that limitation is easily overcome.
    AnalyseMyData(w)
end

Function AnalyseMyData(WAVE w)              // Uses Igor 7 inline declaration style!
    ... Do something with the data in the wave ...
end

elliottmclean wrote:

In regards to the batch fitting I have 2 questions. At the moment I load up the selected files and extract the data into waves and graph the first set of data so I can do an initial fit to test initial guesses. I'm trying to feed W_coef from this inital fit into the batch fitting as the inital guesses for the fit via the Functions and Coefficients sub heading and in the "2D initial guess wave" drop menu. However when I try to run the batch fitting it does not work. It's not a huge inconvenience but it would save me individually typing the guesses into all the boxes.

Quote:

Secondly, on a number of fit that I have run I keep getting an error which reads: "Error on batch X: Limit of passes without decreasing chi-square was reached" and the fit isn't applied to these sets of data and then each data set that follows has an incorrect fit. Now I'm not sure whether this was an error unique to my fitting function or whether it was common for batch fitting in general but I couldn't find a chi-square in my function.

johnweeks wrote:

I'm not sure exactly what you mean- there is nothing in the dialog called "2D initial guess wave". You should be able to make a coefficient wave before you open the dialog, then select that wave from the Coefficient Wave menu. When you do that, the Initial Guess column in the list will be filled in with the contents of your wave. The pre-made coefficient wave must have exactly the right number of elements. Be sure you make a double-precision wave.

Quote:

Secondly, on a number of fit that I have run I keep getting an error which reads: "Error on batch X: Limit of passes without decreasing chi-square was reached" and the fit isn't applied to these sets of data and then each data set that follows has an incorrect fit. Now I'm not sure whether this was an error unique to my fitting function or whether it was common for batch fitting in general but I couldn't find a chi-square in my function.