Help with Pre-allocating function values
显示 更早的评论
Does anyone know how I might be able to go about preallocating f = []; I keep getting hit with the same "arrays dont match" error, I also noticed that if f isnt cleared it tends to add an extra column to the array. Ive noticed this particular portion of my function is extremely slow and it would help alot with the dial im making;
lf = [697 770 852 941]; % Low frequency group
hf = [1209 1336 1477]; % High frequency group
f = [];
for c = 1:4
for r = 1:3
f = [f [lf(c); hf(r)]];
end
end
Thanks,
2 个评论
Dynamically growing arrays is detrimental to the performance of the code. You should Preallocate arrays according to the final output size.
However, you can vectorize this operation -
lf = [697 770 852 941]; % Low frequency group
hf = [1209 1336 1477]; % High frequency group
%% Original method
f = [];
for c = 1:4
for r = 1:3
f = [f [lf(c); hf(r)]];
end
end
f
%% Vectorization method
[x,y] = meshgrid(lf, hf);
F = [x(:) y(:)].'
%Comparison
isequal(f, F)
Mason
2023-11-12
移动：Dyuman Joshi
2023-11-12
采纳的回答
The MATLAB approach:
lf = [697,770,852,941];
hf = [1209,1336,1477];
[X,Y] = meshgrid(lf,hf);
f = [X(:),Y(:)]
Or
T = combinations(lf,hf) % note output is a table!
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Matrices and Arrays 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
