Error in following code while converting cell to matrix

Question

Balaji M. Sontakke 2018-6-21

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https://ww2.mathworks.cn/matlabcentral/answers/406739-error-in-following-code-while-converting-cell-to-matrix

评论： Balaji M. Sontakke 2018-6-22

 Error in following code
 Error using cell2mat (line 52)
 CELL2MAT does not support cell arrays containing cell arrays or objects.
 Error in Fusion_Minutie_InvMoment (line 18)
 fusion = cell2mat(out);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 V = {load('db1.mat'),load('db2.mat'),load('db3.mat'),load('db4.mat')};
 n = cellfun(@fieldnames,V,'un',0);
 V1 = cellfun(@(x,y)[x.(y)]',V,[n{:}],'un',0);
 V2 = [V1{:}];
 V3 = cell2mat(reshape(V2,1200,[]));
 V4 = mat2cell(V3,4*ones(size(V3,1)/4,1),7);
 out = mat2cell(V4,[400,800],1);
 fusion = cell2mat(out);

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Answer 1

Majid Farzaneh 2018-6-21

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Hi, you can do it like this:

V = {load('db1.mat'),load('db2.mat'),load('db3.mat'),load('db4.mat')};
 n = cellfun(@fieldnames,V,'un',0);
 V1 = cellfun(@(x,y)[x.(y)]',V,[n{:}],'un',0);
 V2 = [V1{:}];
 V3 = cell2mat(reshape(V2,1200,[]));
 V4 = mat2cell(V3,4*ones(size(V3,1)/4,1),7);
 out = mat2cell(V4,[400,800],1)
 fusion1 = cell2mat(out{1});
 fusion2= cell2mat(out{2});
 fusion=[fusion1;fusion2];

In your cell matrix (out) there are 2 other cell matrix. For using cell2mat you should have normal matrix in 'out' cell matrix.

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Balaji M. Sontakke 2018-6-22

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Sir, am having the four mat files (attached herewith), which of two contains features from minutiae and other two contains feature from invariant moment. I did classification by loading first two mat files (see following code), In your code (fusion) contains fusion of all mat files, then how i provide the value of reduced_testdata and reduced_traindata for further processing.

 clear all; 
 clc; 
 tic;                  %%calculating elapsed time for execution
 %load mat files
 load('db3.mat');
 load('db4.mat');
 %%reshape into row vector
 reduced_testdata = reshape(reduced_testdata,1,4,100);        
 reduced_traindata = reshape(reduced_traindata,1,4,200);       
 %%adjust dimension
 % Adjust matrix dimension
 P_test = cell2mat(reduced_testdata);                                          % Convert cell array to matrix
 P_train = cell2mat(reduced_traindata); 
 %%rearranges the dimensions of P_test and P_train 
 C = permute(P_test,[1 3 2]);
 P_test = reshape(C,[],size(P_test,2),1);
 C = permute(P_train,[1 3 2]);
 P_train = reshape(C,[],size(P_train,2),1);
 %%labeling class

train_label=load('train_label.txt'); test_label=load('test_label.txt');

 %%Normalisation by Z - Scores 
 P_train = zscore(P_train,0,2);
 P_test  =zscore(P_test,0,2); 
 %%classfication
 predictlabel = knnclassify(P_test, P_train,   train_label,3,'euclidean','nearest');
 cp = classperf(test_label,predictlabel);
 Conf_Mat = confusionmat(test_label,predictlabel);
 disp(Conf_Mat);
 %%Evaluate Performance
 [FPR, TPR,Thr, AUC, OPTROCPT]  = perfcurve(predictlabel, test_label,1);
 figure,
 plot(TPR,FPR,'r-','LineWidth',4);
 xlabel('False positive rate')
 ylabel('True positive rate') 
 title('ROC Curve for Classification ')
 Tbl = table(FPR, TPR,Thr)
 [FPR, FNR, Thr]  = perfcurve(predictlabel, test_label,1,'xCrit','fall','xCrit','miss');
Thr = Thr/10;
 figure,
 plot(Thr,FPR,'r--','LineWidth',2,'MarkerEdgeColor','k','MarkerFaceColor','g','MarkerSize',10);
 xlabel('Threshold')
 ylabel('False positive rate / FAR') 
 title('False Acceptance Rate / FAR ')
 figure,
 plot(Thr,FNR,'r--','LineWidth',2,'MarkerEdgeColor','k','MarkerFaceColor','g','MarkerSize',10);
 xlabel('Threshold')
 ylabel('False Negative rate / FRR') 
 title('False Rejection Rate / FRR ')
 Tbl = table(FPR, FNR,Thr) 
 fprintf('\n\n Overall accuracy:%f%%\n',cp.CorrectRate*100);
 %%calculating elapsed time for execution
 toc

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Answer 2

Andrei Bobrov 2018-6-22

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编辑：Andrei Bobrov 2018-6-22

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fusion = cell2mat(cat(1,out{:}));

or just

V = {load('db1.mat'),load('db2.mat'),load('db3.mat'),load('db4.mat')};
n = cellfun(@fieldnames,V,'un',0);
V1 = cellfun(@(x,y)[x.(y)],V,[n{:}],'un',0);
fusion = cell2mat(reshape(cat(1,V1{:}),1200,[]));