英文:
Find first occurrence of a character in column of a data frame in R
问题
I can help you with the translation:
在R中处理字符串时感到困惑...
我在R数据框中有一列字符串。每个字符串中都包含一次且仅一次的字符"="。我想知道每个列元素中"="字符的位置，这是将该列拆分为两个独立列的步骤之一（一个用于"="之前的部分，另一个用于"="之后的部分）。有人能帮忙吗？我相信这很简单，但我一直在努力寻找答案。
例如，如果我有：
x <- data.frame(string = c("aa=1", "aa=2", "aa=3", "b=1", "b=2", "abc=5"))
我想要一段代码返回：
(3, 3, 3, 2, 2, 4)
谢谢。
英文:
Struggling with string handling in R...
I've got a column of strings in an R data frame. Each one contains the "=" character once and only once. I'd like to know the position of the "=" character in each element of the column, as a step to splitting the column into two separate columns (one for the bit before the "=" and one for the bit after the "="). Can anyone help please? I'm sure it's simple but I'm struggling to find the answer.
For example, if I have:
x <- data.frame(string = c("aa=1", "aa=2", "aa=3", "b=1", "b=2", "abc=5"))
I'd like a bit of code to return
> (3, 3, 3, 2, 2, 4)
Thank you.
答案1
得分: 1
这是一种方法：
library(stringr)str_locate(x$string, "=")[,1]
英文:
Here's a way to do:
library(stringr)str_locate(x$string, "=")[,1]
答案2
得分: 1
在基本的 R 中，您可以执行以下操作：
as.numeric(lapply(strsplit(as.character(x$string), ""), function(x) which(x == "=")))
>[1] 3 3 3 2 2 4
英文:
In Base R you can do:
as.numeric(lapply(strsplit(as.character(x$string), ""), function(x) which(x == "=")))
>[1] 3 3 3 2 2 4
答案3
得分: 1
你可以使用 gregexpr：
unlist(lapply(gregexpr(pattern = ''='', x$string), min))
[1] 3 3 3 2 2 4
英文:
You can use gregexpr:
unlist(lapply(gregexpr(pattern = '=', x$string), min))[1] 3 3 3 2 2 4
答案4
得分: 1
要获取“=”的位置，您可以使用regexp函数：
regexpr("=", x$string)#[1] 3 3 3 2 2 4#attr(,"match.length")#[1] 1 1 1 1 1 1#attr(,"useBytes")#[1] TRUE
但是，正如@Michael所述，如果您的目标是拆分字符串，您可以使用strsplit：
strsplit(x$string, "=")#[[1]]#[1] "aa" "1"#[[2]]#[1] "aa" "2"#[[3]]#[1] "aa" "3"#[[4]]#[1] "b" "1"#[[5]]#[1] "b" "2"#[[6]]#[1] "abc" "5"
或者使用do.call和rbind组合来创建一个新的数据框：
do.call(rbind, strsplit(x$string, "="))# [,1] [,2]#[1,] "aa" "1"#[2,] "aa" "2"#[3,] "aa" "3"#[4,] "b" "1"#[5,] "b" "2"#[6,] "abc" "5"
英文:
To get the position of "=" you can use the regexp function:
regexpr("=", x$string)#[1] 3 3 3 2 2 4#attr(,"match.length")#[1] 1 1 1 1 1 1#attr(,"useBytes")#[1] TRUE
However, as @Michael stated if your goal is to split the string you can use strsplit:
strsplit(x$string, "=")#[[1]]#[1] "aa" "1"##[[2]]#[1] "aa" "2"##[[3]]#[1] "aa" "3"##[[4]]#[1] "b" "1"##[[5]]#[1] "b" "2"##[[6]]#[1] "abc" "5"
Or to combine with do.call and `rbind to create a new dataframe:
do.call(rbind, strsplit(x$string, "="))# [,1] [,2]#[1,] "aa" "1"#[2,] "aa" "2"#[3,] "aa" "3"#[4,] "b" "1"#[5,] "b" "2"#[6,] "abc" "5"
答案5
得分: 1
以下是翻译好的部分：
这是获取一个两列数据框的另一种解决方案，第一列包含等号（=）之前的字符，第二列包含等号之后的字符。您可以在不获取等号位置的情况下完成这个操作。
library(stringr)t(as.data.frame(strsplit(x$string, "=")))# [,1] [,2]#c..aa....1.. "aa" "1"#c..aa....2.. "aa" "2"#c..aa....3.. "aa" "3"#c..b....1.. "b" "1"#c..b....2.. "b" "2"#c..abc....5.. "abc" "5"
英文:
Here is another solution to obtain a two column dataframe, the first containing the characters before = and the second one containing the characters after =. You can do that without obtaining the positions of the = character.
library(stringr)t(as.data.frame(strsplit(x$string, "=")))# [,1] [,2]#c..aa....1.. "aa" "1"#c..aa....2.. "aa" "2"#c..aa....3.. "aa" "3"#c..b....1.. "b" "1"#c..b....2.. "b" "2"#c..abc....5.. "abc" "5"
答案6
得分: 0
一些人可能会觉得这更容易阅读library(tidyverse)x %>%mutate(number = string %>%str_extract('[:digit:]+'),text = string %>%str_extract('[:alpha:]+')) %>%as_tibble()# 一个 tibble: 6 x 3string number text<fct> <chr> <chr>1 aa=1 1 aa2 aa=2 2 aa3 aa=3 3 aa4 b=1 1 b5 b=2 2 b6 abc=5 5 abc
英文:
Some may find this more readable
library(tidyverse)x %>%mutate(number = string %>% str_extract('[:digit:]+'),text = string %>% str_extract('[:alpha:]+')) %>%as_tibble()# A tibble: 6 x 3string number text<fct> <chr> <chr>1 aa=1 1 aa2 aa=2 2 aa3 aa=3 3 aa4 b=1 1 b5 b=2 2 b6 abc=5 5 abc
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