# what does this line means in the following code? I=I(200:400,250:450,:); and when i change the ratio there comes an error of "index exceeds matrix dimensions"

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misbah mateen on 18 Apr 2017
Commented: Image Analyst on 19 Apr 2017
I=I(200:400,250:450,:);% about M1:60second % M2:70second % M3:60second
tic
S=regcovsmooth(I,10,4,0.2,'M1');
toc

Andrew Newell on 18 Apr 2017
Edited: Andrew Newell on 19 Apr 2017
The function imread retrieves a 3D array consisting of 2D images in various colors or grayscale. The number of these images depends on the size of the third dimension (see Multidimensional arrays). They may, for example, be the red, green and blue components of the total color. The command I=I(200:400,250:450,:) is taking a rectangular sample out of each of these images. As for how regcovsmooth deals with it, this is software from GitHub that I'm not familiar with.

misbah mateen on 19 Apr 2017
if i wanna get full image then what should i change in this statement?
Walter Roberson on 19 Apr 2017
For the full image, leave out the line
I=I(200:400,250:450,:);% about M1:60second % M2:70second % M3:60second
Or if you want to leave something there as a placeholder to make it easier to change back, then
I = I(:,:,:);
misbah mateen on 19 Apr 2017
ok. thank you. it works for full image.

msahar on 18 Apr 2017
Edited: msahar on 19 Apr 2017
I am assuming that you are particularly asking about regcovsmooth function. This function is used for preserving image smoothing via region covariances. The output S is the structure component extracted from input image I.

misbah mateen on 19 Apr 2017
thanks for your response. yeah i am doing the project on that research paper. and i am stuck in this line I=I(200:400,250:450,:);.
msahar on 19 Apr 2017
This line just scale the image (i is used to take out the desired portion of image) so that it take the form of positive definite matrix.
misbah mateen on 19 Apr 2017
ok. thank you.

Image Analyst on 18 Apr 2017
regcovsmooth
It probably wants a gray scale image, not a color image. At least that's what I'd try to get rid of the error message.
tic
I = rgb2gray(I);
S = regcovsmooth(I,10,4,0.2,'M1');
By the way, please pick a more descriptive variable name than I. It looks too must like 1 (one) and l (lower case L).

Andrew Newell on 19 Apr 2017
Another option would be to contact the creator of that function.
msahar on 19 Apr 2017