how to correct subscript indices error in following codes?

a=0.85;    
  for i=1:7
  filename=strcat('D:\2nd year\EXP season 2\Dry\cat1\',num2str(i),'.bmp');
  I=imread(filename);
  I1=I(:,:,2);
  I2=I(:,:,3);
  G_Channel_cat1(i-2)=mean(mean(I1(293+(-5:5),285+(-5:5))))-mean(mean(I2(293+(-5:5),285+(-5:5))))*a;
  end

Answer 1

[Walter Roberson]

When i is 1, i-2 is going to be -1, and you cannot store into element number -1 of G_Channel_cat1.

It is not obvious what you are trying to do in that assignment statement, so I cannot suggest any fix other than not subtracting 2 from "i" at that point.

[satish thapaliya]

even on changing value of i from 3 to 9 when i try to plot G-Channel against seven different x values, the problem switchs to undefined function or method for input arguements of type double.

[Walter Roberson]

Please show that part of the code, and show the error message.

[satish thapaliya]

Here is the code and error message

a=0.85;    
    for i=3:9
    filename=strcat('D:\2nd year\EXP season 2\Dry\cat1\',num2str(i),'.bmp');
    I=imread(filename);
    I1=I(:,:,2);
    I2=I(:,:,3);
    G_Channel_cat1(i-2)=mean(mean(I1(293+(-5:5),285+(-5:5))))-mean(mean(I2(293+(-5:5),285+(-5:5))))*a;
    end
    for i=3:9
    filename=strcat('D:\2nd year\EXP season 2\Dry\cat2\',num2str(i),'.bmp');
    I=imread(filename);
    I1=I(:,:,2);
    I2=I(:,:,3);
    G_channel_cat2(i-2)=mean(mean(I1(301+(-5:5),284+(-5:5))))-mean(mean(I2(301+(-5:5),284+(-5:5))))*a;
    end
    for i=3:9
    filename=strcat('D:\2nd year\EXP season 2\Dry\cat3\',num2str(i),'.bmp');
    I=imread(filename);
    I1=I(:,:,2);
    I2=I(:,:,3);
    G_channel_cat3(i-2)=mean(mean(I1(310+(-5:5),283+(-5:5))))-mean(mean(I2(310+(-5:5),283+(-5:5))))*a;
    end
    for i=3:9
    filename=strcat('D:\2nd year\EXP season 2\Dry\cat4\',num2str(i),'.bmp');
    I=imread(filename);
    I1=I(:,:,2);
    I2=I(:,:,3);
    G_channel_cat4(i-2)=mean(mean(I1(320+(-5:5),285+(-5:5))))-mean(mean(I2(320+(-5:5),285+(-5:5))))*a;
    end
    x=[0.121,0.422,0.844,4.219,12.053,21.094,60.267];
    for i=1:7
        y(i)=(G_channel_cat1(i)+G_channel_cat2(i)+G_channel_cat3(i)+G_channel_cat4(i))/4;
    end
    plot(y,x,'r')

??? Undefined function or method 'G_channel_cat1' for input arguments of type 'double'.

[Walter Roberson]

Your first "for" loop assigns to G_Channel_cat1 which has an upper-case C. All your other variables use a lower-case C there.