Write a function called halfsum that takes as input an at most two-dimensional matrix A and computes the sum of the elements of A that are in the diagonal or are to the right of it. example, the input is [1 2 3; 4 5 6; 7 8 9],the ans is 26

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Deepanshu Parihar
Deepanshu Parihar on 28 May 2015
function s = halfsum(A)
[row col] = size(A);
if row ~= col
error('Expecting a square matrix here people...');
end
s = 0;
for ii = 1:row
for jj = ii:col
s = s + A(ii,jj);
end
end
  14 Comments

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Answers (10)


Joseph Cheng
Joseph Cheng on 28 May 2015
your input should be
input = [1 2 3;4 5 6;7 8 9]
and not
input = [1 2 3 4 5 6 7 8 9]
  1 Comment
Joseph Cheng
Joseph Cheng on 28 May 2015
which if you read carefully the problem statement and the code the input is a 3x3 square matrix. the input you provided it was a 1x9 array.

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Srishti Saha
Srishti Saha on 7 Apr 2018
This code works perfectly for me:
%function to compute sum of lower most right side triangle in an X*2 matrix
function u = halfsum(P)
u1 = P(end:-1:1, 1:end);
u2 = triu(u1);
u = sum(u2(:));
end

Ajith Bharadwaj
Ajith Bharadwaj on 3 Feb 2020
function summa = halfsum(A)
[row col] = size(A);
for ii = 1:row
for jj = ii:col
summa = summa + A(ii,jj);
end
end
  5 Comments
Amit Jain
Amit Jain on 3 Nov 2020
I hope this clears your doubt. You did not tell function what to if there is n ==1 means there is column vector. I have made this correction. Now function works fine. Thanks

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ERTIZA HOSSAIN SHOPNIL
ERTIZA HOSSAIN SHOPNIL on 21 May 2020
function summa=halfsum(A)
t=triu(A);
list=sum(t);
s=0;
for n=list
s=s+n;
end
summa=s;
end
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saurav Tiwari
saurav Tiwari on 25 Jun 2020
function summa=halfsum(a)
[m,n]=size(a)
for i=1:m
j=1:n
x(i)=sum(a(i,j))
end
summa=sum(x)
end

youssef boudhaouia
youssef boudhaouia on 27 Jul 2020
A solution with double For-loop:
function summa=halfsum(M)
summa=0;
s=size(M);
for i=1:s(1)
for j=1:s(2)
if j>=i
summa=summa+M(i,j);
else
summa=summa;
end
end
end
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Abdul Quadir Khan
Abdul Quadir Khan on 18 Oct 2020
function summa = halfsum(x)
[row,col] = size(x);
allsum=0;
for n=1:row
for c=n:col
allsum=x(n,c)+allsum;
end
end
summa=allsum;

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