用矢量模式或匹配快速grep，返回所有匹配的列表 [英] Fast grep with a vectored pattern or match, to return list of all matches

问题描述

我想这是微不足道的，我很抱歉，我找不到该怎么做。

我试图戒掉一个循环，所以我尝试向量化过程：
我需要做一些类似于 grep 的事情，但是模式是一个向量。另一个选项是匹配，其中值不仅是第一个位置。

例如数据（这不是真实的数据是怎么样的，另外我会利用它的结构）：

  COUNTRIES = c（奥地利，比利时，丹麦，法国，德国，
爱尔兰，意大利，卢森堡，荷兰，
 葡萄牙，瑞典，西班牙，芬兰，英国）
 
 COUNTRIES_Target = rep（COUNTRIES，times = 4066）
 COUNTRIES_Origin = rep（COUNTRIES，each = 4066）
  

现在，我得到了一个循环：

  var_pointer = list（）
 for（i in 1：length（COUNTRIES_Origin））
 {
 var_pointer [[i]] = which（COUNTRIES_Origin [i] == COUNTRIES_Target）
} 
  

c $ c> match 是 match（x = COUNTRIES_Origin，table = COUNTRIES_Target）返回一个长度与 COUNTRIES_Origin ，值是第一个匹配，而我需要他们所有人。

grep 的问题在于 grep（pattern = COUNTRIES_Origin，x = COUNTRIES_Target）是给定的警告：
警告消息：
在grep中（pattern = COUNTRIES_Origin，x = COUNTRIES_Target）：
参数'pattern'的长度> 1，只有第一个元素会被使用

有什么建议？

解决方案

看起来好像你可以在列表中而不是 loop 。< （COUNTRIES_Origin，function（x）which（COUNTRIES_Target == x））
$ / $>

在这里我使用哪个因为 grep 似乎对部分匹配更好，而您正在寻找完全匹配。

I guess this is trivial, I apologize, I couldn't find how to do it.

I am trying to abstain from a loop, so I am trying to vectorize the process: I need to do something like grep, but where the pattern is a vector. Another option is a match, where the value is not only the first location.

For example data (which is not how the real data is, otherswise I would exploit it structure):

COUNTRIES=c("Austria","Belgium","Denmark","France","Germany",
"Ireland","Italy","Luxembourg","Netherlands",
"Portugal","Sweden","Spain","Finland","United Kingdom")

COUNTRIES_Target=rep(COUNTRIES,times=4066)
COUNTRIES_Origin=rep(COUNTRIES,each=4066)

Now, currently I got a loop that:

var_pointer=list()
for (i in 1:length(COUNTRIES_Origin))
{     
var_pointer[[i]]=which(COUNTRIES_Origin[i]==COUNTRIES_Target)
 }

The problem with match is that match(x=COUNTRIES_Origin,table=COUNTRIES_Target) returns a vector of the same length as COUNTRIES_Origin and the value is the first match, while I need all of them.

The issue with grep is that grep(pattern=COUNTRIES_Origin,x=COUNTRIES_Target) is the given warning: Warning message: In grep(pattern = COUNTRIES_Origin, x = COUNTRIES_Target) : argument 'pattern' has length > 1 and only the first element will be used

Any suggestions?

解决方案

It seems like you can just lapply over the list rather than loop.

lapply(COUNTRIES_Origin, function(x) which(COUNTRIES_Target==x))

Here I use which because grep seems to be better for partial matches and you're looking for exact matches.

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