如何找到连续n个连续零的索引 [英] How to find the indices where there are n consecutive zeroes in a row

问题描述

假设我有以下数据：

  x = c(14,14, 6,  7 ,14 , 0 ,0  ,0 , 0,  0,  0 , 0 , 0,  0 , 0 , 0 , 0,  9  ,1 , 3  ,8  ,9 ,15,  9 , 8, 13,  8,  4 , 6 , 7 ,10 ,13,  3,
 0 , 0 , 0 , 0 , 0 , 0,  0,  0 , 0 , 0 , 0,  0,  0,  0,  0  ,0,  0 , 0 , 0,  0,  0,  0,  0 , 0,  0, 4 , 7  ,4,  5 ,16 , 5  ,5 , 9 , 4  ,4,  9 , 8,  2,  0  ,0  ,0  ,0  ,0,  0,  0,  0  ,0 , 0,  0,  0,  0,  0,  0,  0,  0,0)

x
 [1] 14 14  6  7 14  0  0  0  0  0  0  0  0  0  0  0  0  9  1  3  8  9 15  9  8
[26] 13  8  4  6  7 10 13  3  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
[51]  0  0  0  0  0  0  0  0  4  7  4  5 16  5  5  9  4  4  9  8  2  0  0  0  0
[76]  0  0  0  0  0  0  0  0  0  0  0  0  0  0  

我想恢复索引，该索引从连续3个以上的零开始，到在非零之前的最后0个结束。

I want to recover the indices beginning where there are more than 3 zeroes in a row and terminating with the last 0 before a nonzero.

例如，

我会得到

6，为17

推荐答案

这是两种基本的R方法：

Here are two base R approaches:

1）rle 首先运行 rle ，然后计算 ok 进行选择找出长度超过3的零序列。然后，我们计算所有重复序列的起始和结束，子集设置为 ok

1) rle First run rle and then compute ok to pick out the sequences of zeros that are more than 3 long. We then compute the starts and ends of all repeated sequences subsetting to the ok ones at the end.

with(rle(x), {
  ok <- values == 0 & lengths > 3
  ends <- cumsum(lengths)
  starts <- ends - lengths + 1
  data.frame(starts, ends)[ok, ]
})

给予：

  starts ends
1      6   17
2     34   58
3     72   89

2）gregexpr 取每个数字的符号-将为0或1，然后将它们连接成一个长字符串。然后使用 gregexpr 查找至少四个零的位置。结果给出了起点和终点，可以从中加上 match.length 属性减去1。

2) gregexpr Take the sign of each number -- that will be 0 or 1 and then concatenate those into a long string. Then use gregexpr to find the location of at least 4 zeros. The result gives the starts and the ends can be computed from that plus the match.length attribute minus 1.

s <- paste(sign(x), collapse = "")
g <- gregexpr("0{4,}", s)[[1]]
data.frame(starts = 0, ends = attr(g, "match.length") - 1) + g

给予：

  starts ends
1      6   17
2     34   58
3     72   89

这篇关于如何找到连续n个连续零的索引的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！