How can I make this code simpler

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Jorge Arturo Clares Pastrana
评论： DGM 2022-2-16
r = 5;
A_r5 = (S_Vals(1,1)*u(:,1)*(V(:,1)).')+(S_Vals(2,1)*u(:,2)*(V(:,2)).')+(S_Vals(3,1)*u(:,3)*(V(:,3)).')+(S_Vals(4,1)*u(:,4)*(V(:,4)).')+(S_Vals(5,1)*u(:,5)*(V(:,5)).');
x_5 = uint8(A_r5);
figure(2)
imshow(x_5);

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回答（2 个）

Image Analyst
Image Analyst 2022-2-16
Yes, that's very complicated to look at. I'd break it into more bite-sized terms, like
term1 = whatever
term2 = whatever
A_r5 = term1 * term2 + term3 or whatever.
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DGM
DGM 2022-2-16
Need to transpose V(:,row).'

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DGM
DGM 2022-2-16
编辑：DGM 2022-2-16
Ran in:
Depends what you mean by "simple". Consider the following three options. Method 2 is compact, but it's slower for large inputs. Method 3 is relatively fast for large inputs. Both method 2 and 3 have an advantage in that they can be scaled to more than 5 "pages".
N = 1000; % large inputs
u = rand(N,5);
V = rand(N,5);
S_Vals = rand(5,1);
% original method
a = timeit(@() testA(S_Vals,u,V))
a = 0.0031
% simple permutation and elementwise math
b = timeit(@() testB(S_Vals,u,V))
b = 0.0132
% looped version of original
c = timeit(@() testC(S_Vals,u,V))
c = 0.0012
% time ratio
[a/b a/c]
ans = 1×2
0.2365 2.6443
function testA(S_Vals,u,V)
A_r5 = (S_Vals(1,1)*u(:,1)*(V(:,1)).') ...
+(S_Vals(2,1)*u(:,2)*(V(:,2)).') ...
+(S_Vals(3,1)*u(:,3)*(V(:,3)).') ...
+(S_Vals(4,1)*u(:,4)*(V(:,4)).') ...
+(S_Vals(5,1)*u(:,5)*(V(:,5)).');
end
function testB(S_Vals,u,V)
A_r5 = sum(permute(S_Vals,[3 2 1]).*permute(u,[1 3 2]).*permute(V,[3 1 2]),3);
end
function testC(S_Vals,u,V)
A_r5 = zeros(size(u,1),size(V,1));
for k = 1:size(S_Vals(1))
A_r5 = A_r5 + (S_Vals(k,1)*u(:,k)*(V(:,k)).');
end
end

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