如何在MATLAB中向量化此代码？如果可能的话，我希望矩阵B是一个稀疏矩阵。
%% Y is a matrix l*n
%% X is a matrix k*n
B = [];
for i=1:l
for j=1:n
temp1 = zeros(1,n*l);
temp1((i-1)*n+j) = -1;
temp2 = zeros(1,l*k);
temp2((i-1)*k+1:i*k) = (-Y(i,j)).*(X(:,j)');
B = [B;[temp1,temp2]];
end
end
我不知道如何将这段代码向量化，请帮忙！谢谢！
利用bsxfun进行元素乘法的屏蔽和矢量化计算，这是一种矢量化方法-
%// Create left part of the output that is basically an identity matrix
parte1 = -eye(n*l);
%// Setup right part of output
parte2 = zeros(n*l,l*k);
%// Mask to set elements from the calculations of (-Y(i,j)).*(X(:,j)')
M = bsxfun(@eq,reshape(repmat(1:l,n,1),[],1),reshape(repmat(1:l,k,1),1,[]));
%// OR concisely : M = kron(eye(l),ones(n,k))==1
%// Perform vectorized calculations of (-Y(i,j)).*(X(:,j)') and set those
%// into second part at masked places
parte2(M) = -bsxfun(@times,permute(X,[2,1,3]),permute(Y,[2,3,1]));
%// Finally concatenate those parts for final output
out = [parte1,parte2];
本文收集自互联网，转载请注明来源。
如有侵权，请联系[email protected] 删除。
我来说两句