MATLAB bsxfun或矢量化

Keith D 发表于 Dev

基思·D

我一直在主要使用bsxfun对代码进行矢量化处理，但是遇到了无法完全破解的情况。这是问题的一小部分。我想删除这段代码中的for循环，但是在tempEA行上遇到了麻烦。

Index = [2; 3; 4;];

dTime = [25; 26; 27; 28; 25; 26; 27; 28; 27; 28];
dIndex = [3; 3; 3; 2; 1; 3; 2; 4; 4; 2];
aTime = [30; 38; 34; 39; 30; 38; 34; 39; 34; 39];
aIndex = [4; 2; 5; 4; 5; 4; 4; 2; 2; 4];

EA = zeros(numel(Index));
for i = 1:numel(Index)
    for j = 1:numel(Index)
        tempEA = aTime(Index(i) == dIndex(:,1) & Index(j) == aIndex(:,1));
        if i == j
        elseif tempEA > 0
            EA(i,j) = min(tempEA);
        else
            EA(i,j) = 50;
        end
    end
end

答案应如下所示：

EA =

     0    50    34
    38     0    30
    34    50     0

预先感谢您的帮助。

路易斯·门多

这使用bsxfun; 没有循环。假设您NaN的aTime价值观中没有。

N = numel(Index);
ii = bsxfun(@eq, dIndex.', Index); %'// selected values according to each i
jj = bsxfun(@eq, aIndex.', Index); %'// selected values according to each j
[ igrid jgrid ] = ndgrid(1:N); %// generate all combinations of i and j
match = double(ii(igrid(:),:) & jj(jgrid(:),:)); %// each row contains the matches for an (i,j) combination
match(~match) = NaN; %// these entries will not be considered when minimizing
result = min(bsxfun(@times, aTime, match.')); %'// minimize according to each row of "match"
result = reshape(result,[N N]);
result(isnan(result)) = 50; %// set NaN to 50
result(result<=0) = 50; %// set nonpositive values to 50
result(1:N+1:end) = 0; %// set diagonal to 0

result(result<=0) = 50;仅当您aTime可以包含非正值时，才需要该行。它可以？还是您elseif tempEA > 0只是检查tempEA不为空的一种方法？