How to vectorize a for-loop?
显示 更早的评论
Hello!
I would appreaciate any help vectorizing the for loop below. The problem i cannot solve is how to take out the constants from wdrive and multiply it with the rest, according to the loop below. I want to become better at vectorizing my MATLAB code so I would really appreciate any help! Thanks alot!
%S and R are square matrices (404*404).
%fc is a column vector
wdrive=0:1:800;
a2=zeros(2*dofs,(length(wdrive)));
b2=zeros(2*dofs,(length(wdrive)));
Amp=zeros(1,length(wdrive));
SRS=S*(R\S);
SRfc=S*(R\fc);
for i=1:length(wdrive)
a2(:,i)=(wdrive(i)^2*SRS+R)\(fs-wdrive(i)*SRfc);
b2(:,i)=(R)\(fc+wdrive(i)*S*a2(:,i));
Amp(i)=sqrt(a2(dofs-1,i)^2+b2(dofs-1,i)^2);
end
采纳的回答
I don't think you can vectorize everything, but you can cut down on the operations done inside the loop,
Rfc=R\fc;
SRS=S*(R\S);
SRfc=S*(Rfc);
rhs=bsxfun(@minus,fs,SRfc*wdrive);
for i=1:length(wdrive)
a2(:,i)=(wdrive(i)^2*SRS+R)\rhs(:,i);
end
b2=Rfc+R\S*bsxfun(@times, wdrive, a2);
Amp=abs(a2(dofs-1,:)+i*b2(dofs-1,:));
5 个评论
Samuel Hammarberg
2013-5-18
Samuel Hammarberg
2013-5-18
编辑：Matt J
2013-5-19
Matt J
2013-5-19
Samuel Hammarberg commented:
It would still be sweet if you, somehow, could get rid of the for loop altogether. So if some one could crack that, that would be great!
Thank you very much!
Matt J
2013-5-19
The for-loop isn't slowing you down significantly. You just have a lot of matrix inversions
(wdrive(i)^2*SRS+R)
to do. There's no simplification to this that I can see, unless there is some special structure in S and R that you haven't mentioned.
Matt J
2013-5-19
You could also try parfor, if you have the Parallel Computing Toolbox.
更多回答（1 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息
2013-5-18
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
