plot while using for loops

Hello, I am a beginner in using matlab. I present my image as a 4x4 array and firstly I rescale my image with different intervals, starting from 0 and ending to 20 by step 10.Then, I am trying to get the ROI which is located in the central of my image.After this, I calculate the mean value and the std deviation of this ROI. Finally, I am trying to plot of (interval,mean_value) and (interval,std deviation) for every step of my increased interval. Well, the results of median value and std deviation look correct but my problem is how to plot my results. Does anybody know how to create these plots? (I put my code after this message)

Thanks in advance.

 A=[ 30,31,12, 9,
    17,12,25,10,
    12, 8,17, 9,
    31,12,26,22];
    A=double(A);
 x=size(A,1);y=size(A,2);
   for interval=0:10:20
          max_A=max(max(A));min_A=min(min(A));
          for i=1:x 
              for j=1:y 
                val=A(i,j);
                tone_ival=[(val-min_A)*(interval/(max_A-min_A))];
                B(i,j)=tone_ival;
              end; 
          end; 
           disp(round(B));
           for i=1:1:2
               for j=1:1:2
                  ROI(i,j)=B(((x/2)+(i-1)),((y/2)+(j-1)));
               end;
           end;
           disp(round(ROI));
         %%%calculate mean value
           sum=0;
          for i=1:1:2
             for j=1:1:2
                sum = sum + ROI(i,j);
             end;
          end;
          mean_value = sum / 4;
          disp(mean_value);
      %%%calculate std deviation
         sum_dev = 0;
         for i=1:1:2
            for j=1:1:2
               sum_dev = sum_dev + ((ROI(i,j)- mean_value)^2);
            end;
         end;
         std_dev = ((sum_dev/(4-1))^(1/2));
         disp(std_dev);

end;

Answer 1

[Paulo Silva]

Do you want to plot all in the same axes?

clc;clf;hold all
mean_v=[];
std_d=[];
inter=[];
A=[ 30,31,12, 9
    17,12,25,10
    12, 8,17, 9
    31,12,26,22];
    A=double(A);
 x=size(A,1);y=size(A,2);
   for interval=0:10:20
          max_A=max(max(A));min_A=min(min(A));
          for i=1:x 
              for j=1:y 
                val=A(i,j);
                tone_ival=[(val-min_A)*(interval/(max_A-min_A))];
                B(i,j)=tone_ival;
              end; 
          end; 
           disp(round(B));
           for i=1:1:2
               for j=1:1:2
                  ROI(i,j)=B(((x/2)+(i-1)),((y/2)+(j-1)));
               end;
           end;
           disp(round(ROI));
         %%%calculate mean value
           sum=0;
          for i=1:1:2
             for j=1:1:2
                sum = sum + ROI(i,j);
             end;
          end;
          mean_value = sum / 4;
          disp(mean_value);
      %%%calculate std deviation
         sum_dev = 0;
         for i=1:1:2
            for j=1:1:2
               sum_dev = sum_dev + ((ROI(i,j)- mean_value)^2);
            end;
         end;
         std_dev = ((sum_dev/(4-1))^(1/2));
         disp(std_dev);
         inter=[inter interval];
         mean_v=[mean_v mean_value];
         std_d=[std_d std_dev];
   end

plot(inter,mean_v)
plot(inter,std_d,'r')
xlabel('intervals')
legend('mean values','std dev values',2)

[john]

It was that I was looking for...Thanks

[bym]

you should "accept" Paulo's answer in addition to commenting