MATLAB：当有多个最大值时，如何从“max”获取第一个元素而不是随机索引？

Question

我有以下代码：

[~,ind]=max(Defender.Q,[],6);

Defender.Q是一个巨大的多维矩阵。

当Defender.Q的第6维中有多个最大值时，max函数 给我这些多个最大值中的第一个的索引。我想获得一个索引 在多个最大值之间随机化。有任何想法吗？谢谢你的帮助！

Answer 1

好的，这有点牵扯，但您可以获取所有最大值的索引，然后使用randi和accumarray随机选择一个：

%# (1) Find the maxima

%# if you are interested in the global maximum
%# that may occur multiple times along dimension 6
[maxVal,maxIdx] = max(Defender.Q(:));

%# ALTERNATIVELY

%# if you are interested in local maxima along dimension 6
maxVal = max(Defender.Q,[],6);
maxIdx = find(bsxfun(@eq,Defender.Q,maxVal));

%# (2) pick random maximum for each 5D subarray

%# this assumes that there is no dimension #7 etc
%# In case there is, you need to add a column of ones
%# and then d7 etc to second input of accumarray

%# find row, col, etc subscripts of the maxima
[d1,d2,d3,d4,d5,d6] = ind2sub(size(Defender.Q),maxIdx);

%# create a 5-d array, containing one random index
%# from the maxima along dimension 6, or NaN
randIdx = accumarray([d1,d2,d3,d4,d5],d6,[],@(x)x(randi(length(x))),NaN);