MATLAB: How to access the data when I do surface fitting in Curve Fitting Toolbox 2.0 (R2009a)

curveCurve Fitting Toolboxfittinglowesssftool

I have used SFTOOL for surface fitting. I do not know how to access the fitted Z-data when I use LOWESS as fit type and export the fit to workspace.

Best Answer

When you export the fit to workspace using the default names you will receive an sfit object called “fittedmodel”. To access and compute the Z-data for the fitted surface use MESHGRID to generate X and Y arrays for the surface and then use the sfit object to compute the Z-data:

[X,Y]= meshgrid(x,y);   % x and y are vectors
Z=fittedmodel(X,Y);

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MATLAB: Matlab curve fitting tool automation for selection of fit with minimum sse.

You could certainly write your own function by using the gof output of the "fit" function.

Here is an example that shows you how to use the "fit" to see the Goodness of Fit of different methods. You could store the "gof" values in an array and find the max GoF.

function bestFitName = Gof_Finder( x, y )
    Fits = {'poly1', 'poly2', 'poly3', 'exp1'};
      for i=1:numel(Fits)
          [~,GoFs(i)] = fit( x, y,  Fits{i} );
      end
      [~, minIdx] = min([GoFs.sse]);
      bestFitName = Fits{minIdx};
  end

The above function will return the name of the best fit of the data x and y.

MATLAB: How to display the contour line values from a contour plot generated using the curve fitting tools

If, in the auto-generated code from the gui you specify h (the handler to the plots) as an aditional output variable you can access those data.

    function [fitresult, gof, h] = createFit(x, y, z)
    %CREATEFIT(X,Y,Z)
    %  Create a fit.
    %


    %  Data for 'untitled fit 1' fit:
    %      X Input : x
    %      Y Input : y
    %      Z Output: z
    %  Output:
    %      fitresult : a fit object representing the fit.
    %      gof : structure with goodness-of fit info.
    %
    %  See also FIT, CFIT, SFIT.
    %  Auto-generated by MATLAB on 28-Apr-2017 12:52:15
    %%Fit: 'untitled fit 1'.
    [xData, yData, zData] = prepareSurfaceData( x, y, z );
    % Set up fittype and options.
    ft = fittype( 'lowess' );
    % Fit model to data.
    [fitresult, gof] = fit( [xData, yData], zData, ft, 'Normalize', 'on' );
    % Make contour plot.
    figure( 'Name', 'untitled fit 1' );
    h = plot( fitresult, [xData, yData], zData, 'Style', 'Contour' );
    legend( h, 'untitled fit 1', 'z vs. x, y', 'Location', 'NorthEast' );
    % Label axes
    xlabel x
    ylabel y
    grid on

h is an array and you have to guess which component is the one for the contour plot. In my example it was h(1). That component is the same as in [C, h] = contour(...), and you can use it in the same way. h(1).ContourMatrix has the matrix C that contour would output, and, in particular you can write

clabel(h(1).ContourMatrix, h(1))

to have the contour lines of your plot labelled.

Best Answer

Related Solutions

MATLAB: Matlab curve fitting tool automation for selection of fit with minimum sse.

MATLAB: How to display the contour line values from a contour plot generated using the curve fitting tools

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