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Index in position 2 exceeds array bounds using crossval

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Tessa Kol
Tessa Kol on 20 Oct 2020
Commented: Tessa Kol on 23 Oct 2020
Dear all,
I got the following error when using crossval.
Error using crossval>evalFun (line 488)
The function '@(Xtr,Ytr,Xte)predict(fitlm(Xtr,Ytr(:,2)),Xte)' generated the following error:
Index in position 2 exceeds array bounds (must not exceed 1).
Error in crossval>getLossVal (line 525)
funResult = evalFun(funorStr,arg(1:end-1));
Error in crossval (line 424)
[funResult,outarg] = getLossVal(i, nData, cvp, data, predfun);
This is my code. The X and Y are stored in the attached .mat file.
%% Cross validation
hpartition = cvpartition(81,'Holdout',0.2);
idxTrain = training(hpartition);
Xtr = X(idxTrain,:);
Ytr = Y(idxTrain,:);
idxNew = test(hpartition);
Xte = X(idxNew,:);
for i = 1:2
for j = 1:3
fcn{i,1} = @(Xtr, Ytr, Xte) predict(fitlm(Xtr,Ytr(:,i)), Xte);
fcn{i,2} = @(Xtr, Ytr, Xte) predict(fitrsvm(Xtr,Ytr(:,i)), Xte);
fcn{i,3} = @(Xtr, Ytr, Xte) predict(fitrgp(Xtr,Ytr(:,i)), Xte);
mse(i,j) = crossval('mse', X, Y(:,i),'Predfun',fcn{i,j}, 'kfold',10);
end
end

Accepted Answer

Nagasai Bharat
Nagasai Bharat on 23 Oct 2020
Hi,
The problem in above code was that crossval does the train-test spilt and it takes in the Ytr as column vector but you did provide Ytr are a 2-D Matrix due to which we were getting that array bound error.The below code snippet should resolve and simplify your issue.
load data
% hpartition = cvpartition(81,'Holdout',0.2);
% idxTrain = training(hpartition);
% Xtr = X(idxTrain,:);
% Ytr = Y(idxTrain,:);
% % Ytr_1 = Y(idxTrain,1);
% % Ytr_2 = Y(idxTrain,2);
% idxNew = test(hpartition);
% Xte = X(idxNew,:);
for i=1:2
for j = 1:3
fcn{i,1} = @(Xtr, Ytr, Xte) predict(fitlm(Xtr,Ytr), Xte);
fcn{i,2} = @(Xtr, Ytr, Xte) predict(fitrsvm(Xtr,Ytr), Xte);
fcn{i,3} = @(Xtr, Ytr, Xte) predict(fitrgp(Xtr,Ytr), Xte);
mse(i,j) = crossval('mse', X, Y(:,i),'Predfun',fcn{i,j}, 'kfold',10);
end
For more information you could follow crossval documentation.
  1 Comment
Tessa Kol
Tessa Kol on 23 Oct 2020
Thank for your reply. I discovered indeed that issue was the 2D-matrix. I forgot to close this post after I resolved the issue myself. But thank you so much for providing the answer!

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