how to convert a structure array to numeric matrix

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Asharani Shinde 2017-12-22

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编辑： Stephen23 2017-12-24

I am trying to use fitcsvm function in Matlab 2014a to classify the features. I used Md1=fitcsvm(X,Y) to create a svm model where X is a array of feature images of .mat extension and Y is label array. now I am having error that X should be a numeric matrix.

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Stephen23 2017-12-24

在 MATLAB Online 中打开

Asharani Shinde's "Answer" moved here:

Thank you Stephen sir for reply . I already used load to assign my .mat feature file to X variable. and made the array of .mat file . In work-space it shows the X variable as structure type array. My error is X should be a numeric matrix. so now I need to convert the structure array to numeric matrix to work the fitcsvm builtin function in matlab. I am giving here the code which I am trying to execute.

global lm  tm X nam Y k ltp_lower Md1 lbl r
  co=0;
  u=0;
  lbl=[char];
  r=0;
 X=[];
 Y=[];
TrainF=dir('tst\');
                Train_N = 0;
                nam=[];
               for k = 1:size(TrainF,1)
                      if not(strcmp(TrainF(k).name,'.')|strcmp(TrainF(k).name,'..')|strcmp(TrainF(k).name,'Thumbs.db'))
                         Train_N = Train_N + 1; % Number of all images in the training database
                         nam{Train_N}=TrainF(k).name;
                      end
               end
for lm=1:length(nam)
            tm=nam{lm};     
            load(['tst\',tm]);
              k=ltp_lower;
               k_pts = detectSURFFeatures(k);
             [boxFeatures, k_pts] = extractFeatures(k, k_pts);
            % X=k;
           X(:,:,lm)=boxFeatures;
         r =tm(7);            
         if r=='1'
              lbl{lm} ='I';
         elseif r=='2'
              lbl{lm} = 'II';
         elseif r=='3'
              lbl{lm} = 'III';
         elseif r=='4'
              lbl{lm} = 'IV';
         elseif r=='5'
              lbl{lm} = 'V';
         elseif r=='6'
              lbl{lm} = 'VI';
         elseif r=='7'
              lbl{lm} = 'VII';
         elseif r=='8'
              lbl{lm} ='VIII';
         elseif r=='9'
              lbl{lm} = 'XI';   
         end
         Y=lbl ;
         Y=categorical(Y);
        Md1=fitcsvm(X,Y);                 
  end

Stephen23 2017-12-24

Asharani Shinde's comment moved here:

Thus pls suggest me proper way to train the SVM and how to give test image to trained classifier and what will be the output? either it will give me matching class or matching image to query image.

Stephen23 2017-12-24

编辑：Stephen23 2017-12-24

"In work-space it shows the X variable as structure type array"

You might just need to get one of the fields of X. Learn about structures by reading the MATLAB documentation:

https://www.mathworks.com/help/matlab/structures.html

especially the part on how to access the data in a structure.

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how to convert a structure array to numeric matrix

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