Symbolic summation within a for-loop
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Robert Mason
on 22 Jul 2016
Answered: Azzi Abdelmalek
on 22 Jul 2016
I have a function that is dependent on two variables, f(j, k). I would like to create a loop that, for each j, sums the function for each value of k. I have tried the code:
for j=1:10;
g(j)=symsum(f(j,k), k, 1, 10);
end;
However, I get an error message "Undefined function 'symsum' for input arguments of type 'double'." on running the code. What is the best way to do the above in MATLAB?
Accepted Answer
Walter Roberson
on 22 Jul 2016
symsum cannot use the summation variable to index.
If f is not vectorized then you use
sum( arrayfun(@(k) f(j, k), 1:10) )
If f is vectorized you might be able to use
sum( f(j, 1:10) )
but you might need
sum( f(repmat(j,1,10), 1:10) )
depending on how f is coded.
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More Answers (1)
Azzi Abdelmalek
on 22 Jul 2016
Look at this example
syms f j k
f=j*sin(k)
for jj=1:10;
ff(k)=subs(f,j,jj);
s=symsum(ff(k), k, 1, 10);
g(jj)=double(s)
end;
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