Find the sum of the non perimeter elements of a matrix using a for loop

1 view (last 30 days)
I have this matrix
B=[-3 4 7;9 11 -13;-17 19 -23;-29 31 37;39 41 47]
and I need to find the sum of the non perimeter elements using a for loop. I can find the sum of a single column or row or of the whole matrix, but I don't know how to write a loop to only sum the 3 non perimeter numbers. Any help is appreciated, thank you.

Accepted Answer

Image Analyst
Image Analyst on 24 Apr 2016
Edited: Image Analyst on 24 Apr 2016
Try it this way:
B=[-3 4 7;9 11 -13;-17 19 -23;-29 31 37;39 41 47]
[rows, columns] = size(B)
theSum = 0;
for col = 2 : columns - 1
for row = 2 : rows-1
theSum = theSum + B(row, col);
end
end
fprintf('The sum = %f\n', theSum);
  2 Comments
Vinny
Vinny on 24 Apr 2016
Thank you! How about if I wanted it to find the sum of the perimeter elements?
Image Analyst
Image Analyst on 24 Apr 2016
Hopefully you're not just asking me to do all your homework for you. Here is one way:
B=[-3 4 7;9 11 -13;-17 19 -23;-29 31 37;39 41 47]
[rows, columns] = size(B)
theSum = 0;
for col = 1 : columns
for row = 1 : rows
if row == 1 || row == rows || col == 1 || col == columns
% It's on the perimeter of the array.
theSum = theSum + B(row, col)
end
end
end
fprintf('The sum = %f\n', theSum);

Sign in to comment.

More Answers (2)

Azzi Abdelmalek
Azzi Abdelmalek on 24 Apr 2016
Edited: Azzi Abdelmalek on 24 Apr 2016
A=B
A(:,[1 end])=0
A([1 end],:)=0
out=sum(A(:))

Ibrahim Abouemira
Ibrahim Abouemira on 19 May 2019

Categories

Find more on Multidimensional Arrays in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!