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Summation of specific range of 2d array

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Meenal Shah
Meenal Shah on 12 May 2020
Edited: Meenal Shah on 13 May 2020
I have a grayscale image image named tumour.
I need to find the area where the intensity is greater than 0.
I have another variable outline showing the outline of original image.
G1 is an empty array.
To find it properly, I have used this code:
for i=1:200
for j=1:200
if((outline(i,j)>0) && sum(sum(tumor(i-5,j-5),tumor(i+5,j+5)))>0)
I want to get the outline of only the tumour.
However, I am getting this error (in the sum() part) and I am unable to solve it:
Error using sum
Dimension argument must be a positive integer scalar, a vector of unique positive integers, or 'all'.


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Accepted Answer

Mehmed Saad
Mehmed Saad on 12 May 2020
Edited: Mehmed Saad on 12 May 2020
I donot understand what you are trying to do in the code. There are much simpler ways to do it.
By looking in your code i think the error is occuring because your for loop index starts from i=1 and ends at i= 200. When you access i-5 or j-5 it will give error because you are indexing negative values to tumor. SImilarly when your loop reaches end it will try to access 200+5 which is out of bound. So run you for loop from
and i think what you are intended to do in this line is accessings tumor's i-5th to i+5th index and j-5th to j+5th index( i.e. total 11x11 elements) . AM i right?


Meenal Shah
Meenal Shah on 12 May 2020
I basically wish to get the sum of block of 10x10 cells. I wish to then check if the sum of this entire block is greater than 0.
Also, I tried editing the code as you said, but it showed no change in the error.
Thank you for helping me.
Mehmed Saad
Mehmed Saad on 12 May 2020
Try to generate 10x10 array from tumor For example tumor(1:10,1:10)
Now try to index it in two for loops of yours such that index doesnot exceed tumor dimension
Meenal Shah
Meenal Shah on 13 May 2020
Thank you so much. It worked when I tried doing that.
Hope you stay safe.

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