这个想法是对向量进行排序，并取中间值。 对于偶数长度的向量，我们计算中间两个值的平均值。
例：
%# some random vector
%#x = rand(99,1); %# odd-length
x = rand(100,1); %# even-length
%# index/indices for median value
num = numel(x);
[~,ord] = sort(x);
idx = ord(floor(num/2)+(rem(num,2)==0):floor(num/2)+1);
%# median value
med = mean( x(idx) );
%# compare against MATLAB's function
median(x)
编辑
这是一个示例函数实现：
function [med idx] = mymedian(x)
%# MYMEDIAN
%#
%# Input: x vector
%# Output: med median value
%# Output: idx corresponding index
%#
%# Note: If vector has even length, idx contains two indices
%# (their average is the median value)
%#
%# Example:
%# x = rand(100,1);
%# [med idx] = mymedian(x)
%# median(x)
%#
%# Example:
%# x = rand(99,1);
%# [med idx] = mymedian(x)
%# median(x)
%#
%# See also: median
%#
assert(isvector(x));
[~,ord] = sort(x);
num = numel(x);
if rem(num,2)==0
%# even
idx = ord(floor(num/2):floor(num/2)+1);
med = mean( x(idx) );
else
%# odd
idx = ord(floor(num/2)+1);
med = x(idx);
end
end
