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Symbolic summation within a for-loop

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Robert Mason
Robert Mason 2016-7-22
回答： Azzi Abdelmalek 2016-7-22
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?

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采纳的回答

Walter Roberson
Walter Roberson 2016-7-22
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.

更多回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2016-7-22
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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