有人可以告诉我此功能的实际作用吗? [英] Can someone tell me what this function actually does?

问题描述

我是MATLAB的新手，我想知道此函数的实际作用.该函数是从上一个问题中复制来的，该问题帮助我解决了连续查找数字频率的问题.

Hi i'm new to MATLAB and i was wondering what this function actually does. The function was copied from a previous question that helped me out with a problem to find the frequency of a number in a row.

链接: 一系列连续的数字(不同长度)

d=[3 2 4 2 2 2 3 5 1 1 2 1 2 2 2 2 2 9 2]
q = diff([0 d 0] == 2);
v = find(q == -1) - find(q == 1);

推荐答案

让我们一步一步地了解它.

Lets get to it step by step.

您有一个数组d:

d=[3 2 4 2 2 2 3 5 1 1 2 1 2 2 2 2 2 9 2]

您申请了它

q = diff([0 d 0] == 2);

这采用[0 d 0] == 2的派生词.基本上，它取所有2的数字的导数.[0 d 0] == 2的结果是:

This takes the derivative of [0 d 0] == 2. Basically it takes the derivative of all the numbers that are 2. The result of [0 d 0] == 2 is:

0 0 1 0 1 1 1 0 0 0 0 1 0 1 1 1 1 1 0 1 0

您可以看到，当原始向量中有2时，便有1；在乞gg中有0，最后有0.如果我们用q = diff([0 d 0] == 2)取它的导数:

You can see that there are 1 whenever there was a 2 in the original vector, and it has a 0 in the begging and a 0 in the end. If we take the derivative of this by q = diff([0 d 0] == 2):

q =

     0 1 -1 1 0 0  -1 0 0 0 1 -1 1 0 0 0 0 -1 1 -1

每当原始向量中出现2时，您将获得1；而当消失时，则为-1.最后一行仅分别查找1和-1，然后减去它们出现的索引，这样您现在就可以知道它们之间有多少个数字.由于1表示数字2开始"，而-1表示行中没有第二个数字"，这将为您提供一系列连续2的长度.

You get 1 whenever a 2 in the original vector appeared and a -1 when in disappeared. The last line finds just the 1 and just the -1 separately and substract the indices where they appeared, that way you can now how many numbers are between them. As 1 means "number 2 starts" and -1 means "no more number 2s in a row" this will give you the length of the series of 2s in a row.

v = find(q == -1) - find(q == 1);

v=
    1     3     1     5     1

开头有一个2，然后是3个2，然后是另一个，然后是5，最后是9，最后是一个.

There is a single 2 in the begining, then there is a series of 3 2s, then another single one, then 5 come and separated by a 9, the last one comes.

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