Matlab: Working for-loop breaks in parfor while fitting curves

Question

Hoping you may be able to assist me with this error. I am running some code to fit curves to ages using a cross validation regime. I iterate the curve fitting 1000 times to assess the best fit.

I define my models as:

linear_ft = fittype({'x', '1'});
monotonic_ft= fittype({'-1/x', '1'});
quadratic_ft = fittype('poly2'); 

I then run the following to iterate through different selections of data splitting, recording the residuals following the curve fit...

Data = randn(4,300,10,10);
Ages = randn(300,1);

for thisDim1 = 1:4
    for thisDim2 = 1:10
        for thisDim3 = 1:10
            for nIts = 1:1000
                RandomOrder = randperm(300,300);
                Fit_Subs = RandomOrder(1:length(Ages)/2); % Take random subs to fit to
                Test_Subs = RandomOrder(length(Ages)/2+1:300); % Take random subs to test fit to

                Fit_Data = squeeze(Data(thisDim1,Fit_Subs,thisDim2,thisDim3)); % Take data to fit to
                Test_Data = squeeze(Data(thisDim1,Test_Subs,thisDim2,thisDim3)); % Take data to test fit

                Fit_Ages = Ages;
                Fit_Ages(Fit_Subs) = []; %Take ages of Fit Subs only
                Test_Ages = Ages;
                Test_Ages(Test_Subs) = []; % Take ages of Test Subs only

                Nsubs = (length(Ages)/2);

                % Model Data using Curves
                fFit_Lin = fit(Fit_Ages,Fit_Data',linear_ft);
                fFit_Mon = fit(Fit_Ages,Fit_Data',monotonic_ft);
                fFit_Quad = fit(Fit_Ages,Fit_Data',quadratic_ft);

                % Fit Modelled Data to Test Data
                tFit_Lin = fFit_Lin(Test_Ages);
                tFit_Mon = fFit_Mon(Test_Ages);
                tFit_Quad = fFit_Quad(Test_Ages);

                % Calculate Median Residual
                Lin_Med_Resid(nIts) = median(tFit_Lin - Test_Data');
                Mon_Med_Resid(nIts) = median(tFit_Mon - Test_Data');
                Quad_Med_Resid(nIts) = median(tFit_Quad - Test_Data');

            end
        end
    end
end

If you run this with the fourth loop (nIts) as a for-loop it will run. If you run it as a parfor-loop it won't stating the error:

Error using fit>iFit (line 264) The name 'lower' is not an accessible property for an instance of class 'llsqoptions'.

Error in fit (line 108) [fitobj, goodness, output, convmsg] = iFit( xdatain, ydatain, fittypeobj, ...

Does anyone have any idea how to fix this? I would be most grateful for any advice!!

Thanks,

Ben

Answer 1

Try restarting MATLAB or typing clear all to see if it clears things up for you.

Your code works for me, but the parallel toolbox can be a bit finicky in my experience.