For loop Issue, Loops, Row Col Indexing Issue

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rizwan 2015-4-7

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关闭： MATLAB Answer Bot 2021-8-20

Experts, I stuck in the logic of for loop,

    load 'D:\MS\Research\Classification Model\Research Implementation\test.mat'; % loading test data i.e cp
    [rI,cI]               =   size(cp);% size of test data
    resultantImage        =   zeros(rI,cI);  % image to store classified pixels
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  for i=1:length(resultantImage)  
      classes           =   svmclassify(SVMModel,cp(rI(i),cI(i)),'Showplot', true);
      if (classes == 'Y')
               resultantImage(rI(i),cI(i)) = 1;
          classes = 1;
      else if (classes == 'N')
              resultantImage(rI(i),cI(i)) = 0;
          end
      end
  end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

In the above for loop i want to extract the value from 'cp' variable and pass it to classifier for classification once i have pixel classified as 'Y' or 'N', i use the row col index of the pixel and store either 1 or 0 at the same row col index of resultant image. I have written the above logic but resultant image is not getting populated with 1 or 0 values it remains zeros array!!!!!!!!! Please help

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Answer 1

Ingrid 2015-4-7

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This does not seem to be a problem with the for-loop. Are you sure that the SVMM model is correct and that it gives as output 'Y' and 'N' as possible groups? You can check for this by not using an if but a switch so in your case:

for i=1:length(resultantImage)  
      classes           =   svmclassify(SVMModel,cp(rI(i),cI(i)),'Showplot', true);
      switch classes
             case 'Y'
                    resultantImage(rI(i),cI(i)) = 1;
             case 'N'
                    resultantImage(rI(i),cI(i)) = 0;
             otherwise
                    error('Not classified in the correct class')
      end
  end

I always use the switch option when working with string variables as it makes the code more clear to read even if there are no problems in the implementation

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rizwan 2015-4-7

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This is what i want to do

clc;
clear all;
%%%%%%%%%%%%%svm training%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
data                  =   [60  61  62  63  64  65  66  67  68  69  70  71  72  73  74  75  76  77  78  79  80  81  82  83  84  85  86  87  88  89  90  91  92  93  94  95  96  97  98  99  100  101  102  103  104  105  106  107  108  109  110  111  112  113  114  115  116  117  118  119  120  121  122  123  124  125  126  127  128  129  130  131  132  133  134  135  136  137  138  139  140  141  142  143  144  145  146  147  148  149  150  151  152  153  154  155  156  157  158  159  160  161  162  163  164  165  166  167  168  169  170  171  172  173  174  175  176  177  178  179  180  181  182  183  184  185  186  187  188  189  190  191  192  193  194  195  196  197  198  199  200  201  202  203  204  205  206  207  208  209  210  211  212  213  214  215  216  217  218  219  220  221  222  223  224  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  225  226  227  228  229  230  231  232  233  234  235  236  237  238  239  240  241  242  243  244  245  246  247  248  249  250  251  252  253  254  255];
label                 =   ['Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';'Y';   'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';'N';];
species               =   cellstr(label);
groups                =   ismember(species,'Y');
SVMModel              =   svmtrain(data,label,'showplot',true,'kernel_function','rbf');
%%%%%%%%%%%%%svm training%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%svm Testing%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
load 'D:\MS\Research\Classification Model\Research Implementation\test.mat'; % loading test data i.e cp
[rI,cI]               =   size(cp);% size of test data
[a , t] = find(cp ~= 0);
resultantImage        =   zeros(rI,cI);  % image to store classified pixels
*for i=1:length(a)  %loop to classify pixel and store 1 or 0 at the same row col index as it exist in the cp    
      ss = cp(a(i),t(i));
      classes           =   svmclassify(SVMModel,cp(a(i),t(i)),'Showplot', true);
      classes
      i
      switch classes
               case 'Y'
                      resultantImage(a(i),t(i)) = 1;
               case 'N'
                      resultantImage(a(i),t(i)) = 0;
               otherwise
                      error('Not classified in the correct class')
        end
  end
    imtool(resultantImage);

But above loops runs fine for me but it is too much slow , is there any way to speed this for loop?

Ingrid 2015-4-8

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you do not need to use the for-loop, vectorizing your solution would be much faster. This would look something like this

resultantImage = zeros(size(cp));
allClasses = svmclassify(SVMModel, cp, 'Showplot',true);
idx = (strcmpi(allClasses,'Y'));
resultantImage(idx) = 1;

rizwan 2015-4-11

Thanks,

But when i did this it prompts

The number of columns in TEST and training data must be equal.

Please help

For loop Issue, Loops, Row Col Indexing Issue

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