How to complete summation with column vectors?

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Branden Chamness
Branden Chamness 2015-4-29
评论： Stephen23 2015-4-29
I have the following summation I need to complete. x is a column vector of Nx1 and and u is an Nx1 column vector as well. i_th component is given as below and j_th component is same. My question is firstly, do I sum only jth components since summation bounds are j=1 to N? How is this done in Matlab?
I have the code below but I have been doubting it for the last week as the rest of my code has not converged well.
N=10;
x = ones(N,1)
u=1:N
u=u'
u=(u-.5)/N %given parameter of u
in = @(x) sum((u.*x)./(u + u))

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回答（2 个）

Andrei Bobrov
Andrei Bobrov 2015-4-29
编辑：Andrei Bobrov 2015-4-29
Let your vectors this:
x = ones(10,1);
u = ((1:10)'-.5)/10;
Solution:
[ui,uj] = ndgrid(u);
out = ui./(ui+uj)*x(:);
Gopalkrishna Bhat
Gopalkrishna Bhat 2015-4-29
try the below code for N=4. Assuming that k is the 2nd column and there are only 4 rows.
sum=0; ui=1; k=1;
for j=1:4 sum=sum+(ui*u(j,k))/(ui+u(j,k)); end
  1 个评论
Stephen23
Stephen23 2015-4-29
Never call a variable sum, as this is the name of an inbuilt function sum. This is a really bad idea, do not do this.

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