Simplification of "for" loop MATLAB R2018a
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GIorgi Tsutskiridze
on 26 Apr 2018
Commented: GIorgi Tsutskiridze
on 26 Apr 2018
I want to perform the following procedure:
I have two vectors x=[1,2,3] and y=[5,7,9]
I want to take first element of x and then add each element from y to it, then I want to take second element from x and add each element from y to it and so on... Finally, I want to save each result from each step of this procedure in a vector of the corresponding size. I know in advance that I will get the following vector r =[6,8,10,7,9,11,8,10,12].
In order to perform the following procedure I have written the following script:
clear
a = 1;
b = 3;
c = 5;
d = 2;
e = 9;
x = [a:b];
y = [c:d:e];
[rx,cx] = size(x);
[ry,cy] = size(y);
r = zeros((cx*cy),1);
for ii = x
for jj = y
xi = find(x==ii)
yi = find(y==jj)
row = xi*cy-(cy-yi)
r(row) = ii + jj
end
end
Finally, I got the result but I spent about 2 hours to come up with that. (well, I am just beginner in programming). I would be happy to know if there is any simpler and more efficient way to do that. I am especially concerned about this step, since it took the most of my time. Or should I give up coding since I took for so long for so simple problem?
xi = find(x==ii)
yi = find(y==jj)
row = xi*cy-(cy-yi)
r(row) = ii + jj
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Accepted Answer
Birdman
on 26 Apr 2018
Edited: Birdman
on 26 Apr 2018
By the power of implicit expansion starting from R2016b in MATLAB, your desire can be achieved in one line of code:
r=reshape((x.'+y).',1,[])
Read the following blog to understand implicit expansion:
Note that (x.'+y).' part refers to implicit expansion. Since they have a dimension mismatch, MATLAB internally adjusts their dimensions to allow them to be summed.
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