计算数组中的重复整数

本文介绍了计算数组中的重复整数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

如果我有这个向量:

x = [1 1 1 1 1 2 2 2 3 4 4 6 6 6 6]

我想根据自己的位置获取每个唯一编号的位置.

I would like to get the position of each unique number according to itself.

y = [1 2 3 4 5 1 2 3 1 1 2 1 2 3 4]

目前我正在使用:

y = sum(triu(x==x.')) % MATLAB 2016b and above

它很紧凑，但内存效率显然不高.

It's compact but obviously not memory efficient.

为了使MATLAB编程具有纯粹的美感，我将避免使用循环.您是否有更好的简单实现?

For the pure beauty of MATLAB programming I would avoid using a loop. Do you have a better simple implementation ?

上下文:

我的最终目标是对向量x进行排序，但受到一个约束，即出现次数N的数字要优先于出现次数超过N的另一个数字:

My final goal is to sort the vector x but with the constraint that a number that appear N times has the priority over another number that has appeared more than N times:

[~,ind] = sort(y); x_relative_sort = x(ind); % x_relative_sort = 1 2 3 4 6 1 2 4 6 1 2 6 1 6 1

推荐答案

假定x已排序，这是使用 unique ， diff 和 cumsum :

Assuming x is sorted, here's one vectorized alternative using unique, diff, and cumsum:

[~, index] = unique(x); y = ones(size(x)); y(index(2:end)) = y(index(2:end))-diff(index).'; y = cumsum(y);

现在您可以应用最终排序:

And now you can apply your final sorting:

>> [~, ind] = sort(y); >> x_relative_sort = x(ind) x_relative_sort = 1 2 3 4 6 1 2 4 6 1 2 6 1 6 1