Info
此问题已关闭。 请重新打开它进行编辑或回答。
Vectorization and a strange result
2 次查看(过去 30 天)
显示 更早的评论
Hi,
I am struggling since few hours with a vectorized operation.
I have some vector quantities, and I wanted to vectorize. I put in the attachment a .mat file.
For testing, I compute the fx1 and fx_1 in this way
fx1 = const_1 .* exp(-1j.*beta(1:2)'.*const_2)./const_2 .* t;
fx_1 = const_1 .* exp(-1j.*beta(1)*const_2)./const_2 .* t;
where beta is a vector. I would expect that the first row of fx1 and fx_1 coincide, but they don't. I am very confused what I am missing here. Ideally, I would like to do this
fx1 = const_1 .* exp(-1j.*beta'.*const_2)./const_2 .* t;
instead of multiplying in a for loop for each beta(i).
0 个评论
回答(1 个)
Star Strider
2020-10-14
Your ‘mytest.mat’ file contains:
fx_1: [1×150 double]
beta: [1×25 double]
t: [1×150 double]
const_1: [1×150 double]
const_2: [1×150 double]
fx1: [2×150 double]
It would help to know what you want to do with those vectors and the ‘fx1’ matrix. That is not obvious from the code you posted.
4 个评论
Star Strider
2020-10-15
You are computing ‘fx’ differently in the looop than in the vectorised calculation.
If you plot them:
for i = 1 : length(beta)
fx(i,:) = const_1 .* exp(-1j.*beta(i).*const_2)./const_2 .* t;
end
figure
mesh(abs(fx))
set(gca, 'ZScale','log')
xlabel('t')
ylabel('\beta (index)') % ‘beta’ Is Complex, So Plotting The Index Values
zlabel('|fx1|')
you will see that they are essentially just mirror-images of each other with respect to the z-axis. The magnitudes are of courrse different, the vectorised approach goes from
to
, and the loop goes from
to
. Chioose whatever version makes sense in the context of what you want to do. I have no idea what that is.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/380933/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/380938/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/380943/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/380948/image.png)
I would use the fully-vectorised approach (in my code), since to me that makes more sense.
此问题已关闭。
另请参阅
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!