使用 gsub 或 sub 函数只获取字符串的一部分？

Question

      Col
WBU-ARGU*06:03:04
WBU-ARDU*08:01:01
WBU-ARFU*11:03:05
WBU-ARFU*03:456

我有一列有 75 行变量，例如上面的 col。我不太确定如何使用 gsub 或 sub 来获取第一个冒号之后的整数。

预期输出：

      Col
WBU-ARGU*06:03
WBU-ARDU*08:01
WBU-ARFU*11:03
WBU-ARFU*03:456

我试过了，但似乎不起作用：

gsub("*..:","", df$col)

Answer 1

您可以使用

df$col <- sub("(\d:\d+):\d+$", "\1", df$col)

见regex demo

详情

(\d:\d+) - 捕获第 1 组（其值可通过替换模式中的 </code> 访问）：一个数字、一个冒号和 1+ 个数字。</li> <li><code>: - 冒号
\d+ - 1+ 位数
$ - 字符串结尾。

R Demo:

col <- c("WBU-ARGU*06:03:04","WBU-ARDU*08:01:01","WBU-ARFU*11:03:05","WBU-ARFU*03:456")
sub("(\d:\d+):\d+$", "\1", col)
## => [1] "WBU-ARGU*06:03"  "WBU-ARDU*08:01"  "WBU-ARFU*11:03"  "WBU-ARFU*03:456"

替代方法：

df$col <- sub("^(.*?:\d+).*", "\1", df$col)

见regex demo

这里，

^ - 字符串开头
(.*?:\d+) - 第 1 组：任何 0+ 个字符，尽可能少（由于惰性 *? 量词），然后是 : 和 1+ 个数字
.* - 字符串的其余部分。

但是，它应该与PCRE正则表达式引擎一起使用，通过perl=TRUE:

col <- c("WBU-ARGU*06:03:04","WBU-ARDU*08:01:01","WBU-ARFU*11:03:05","WBU-ARFU*03:456")
sub("^(.*?:\d+).*", "\1", col, perl=TRUE)
## => [1] "WBU-ARGU*06:03"  "WBU-ARDU*08:01"  "WBU-ARFU*11:03"  "WBU-ARFU*03:456"

参见R online demo。

Answer 2

sub("(\d+:\d+):\d+$", "\1", df$Col)
[1] "WBU-ARGU*06:03"  "WBU-ARDU*08:01"  "WBU-ARFU*11:03"  "WBU-ARFU*03:456"

或者用 stringi:

匹配你想要的（而不是替换掉你不想要的）

stringi::stri_extract_first(df$Col, regex = "[A-Z-\*]+\d+:\d+")

稍微简洁一些stringr:

stringr::str_extract(df$Col, "[A-Z-\*]+\d+:\d+")
# or
stringr::str_extract(df$Col, "[\w-*]+\d+:\d+")

Answer 3

以下内容也可能对您有所帮助。

sub("([^:]*):([^:]*).*","\1:\2",df$dat)

输出结果如下。

> sub("([^:]*):([^:]*).*","\1:\2",df$dat)
[1] "WBU-ARGU*06:03"   "WBU-ARDU*08:01"   "WBU-ARFU*11:03"   "WBU-ARFU*03:456b"

其中数据框的输入如下。

dat <- c("WBU-ARGU*06:03:04","WBU-ARDU*08:01:01","WBU-ARFU*11:03:05","WBU-ARFU*03:456b")
df <- data.frame(dat)

说明： 以下仅作说明之用。

sub("      ##using sub for global subtitution function of R here.
([^:]*)     ##By mentioning () we are keeping the matched values from vector's element into 1st place of memory(which we could use later), which is till next colon comes it will match everything.
:           ##Mentioning letter colon(:) here.
([^:]*)     ##By mentioning () making 2nd place in memory for matched values in vector's values which is till next colon comes it will match everything.
.*"         ##Mentioning .* to match everything else now after 2nd colon comes in value.
,"\1:\2"  ##Now mentioning the values of memory holds with whom we want to substitute the element values \1 means 1st memory place \2 is second memory place's value.
,df$dat)    ##Mentioning df$dat dataframe's dat value.

使用 gsub 或 sub 函数只获取字符串的一部分？

Using gsub or sub function to only get part of a string?

regex

r

gsub