从matlab中的矩阵中找到不是最频繁的数字

Question

我想从 matlab 中每一列的矩阵中找出不是最频繁的数字

例如..，

 a = [3 3 1 4; 0 0 1 1; 0 1 2 4]

我期待的答案是

[3 3 2 1]

任何帮助将不胜感激。

提前致谢。

问候，

拉贾

Answer 1

假设如果tie 用于列中的最小计数，您将选择最小值元素，这是一个基于 bsxfun 的解决方案代码来解决它 -

%%// Unique values across the entire matrix
unqval = unique(a(:))

%// Counts of those unique values for each column
counts = sum(bsxfun(@eq,a,permute(unqval,[3 2 1])),1)

%// Make the zero counts as NaNs as they don't exist at all for a column
counts(counts==0)=NaN

%// Indices for the minimum counts with the minimum valued element in a tie-case
[~,v2] = nanmin(permute(counts,[3 2 1]))

%// Minimum count elements of input for each coloumn, to form the desired output
out = unqval(v2).'

---

使用for-loop 的替代方法-

alf(1,size(a,2))=0; %// alf would be the desired output
for k = 1:size(a,2)
    unqval = unique(a(:,k));
    [~,ind] = min(histc(a(:,k),unqval));
    alf(k) = unqval(ind);
end

Answer 2

这给出了平局时的最低值：

u = unique(a(:)).'; %'// find unique values of a
h = histc(a, u); %// count for each value, in each column
h(h==0) = inf; %// mark non-present values
[~, r] = min(h); %// find first (i.e. lowest) value with minimum count
result = u(r); %// build result