如何提取在 R 中一个字符之后和最后一次出现另一个字符之前发生的所有内容？

Question

我有如下所示的三个字符串：

"GO:0016559~peroxisome fission,"
"GO:0006122~mitochondrial electron transport, ubiquinol to cytochrome c,"
"GO:0006122~mitochondrial electron transport, ubiquinol to cytochrome c,GO:0006334~nucleosome assembly,"

如何提取在“~”之后和“,”之前出现的所有子字符串（字符串的末尾或后跟 GO:.........,)？

期望的输出：

"peroxisome fission"
"mitochondrial electron transport, ubiquinol to cytochrome c"
"mitochondrial electron transport, ubiquinol to cytochrome c" "nucleosome assembly"

这将在 R 中的一个通用语句中实现。

我试过用这个：

strapplyc(str, "[~](.*?)[,]", simplify = c)

（其中 str 是一个变量，它循环存储三个字符串中的每一个，一次一个）

但是我得到的输出是：

"peroxisome fission"
"mitochondrial electron transport"
"mitochondrial electron transport" "nucleosome assembly"

Answer 1

您可以使用

(?<=~).*?(?=,(?:GO:\d+~|$))

见regex demo。详情:

(?<=~) - ~ char
.*? - 除换行字符外的任何零个或多个字符，尽可能少
(?=,(?:GO:\d+~|$)) - 正向前瞻，需要一个逗号，然后是 GO:、一个或多个数字和 ~ 或紧靠当前位置右侧的字符串结尾。

看到 R demo:

> library(stringr)
> x <- c("GO:0016559~peroxisome fission,","GO:0006122~mitochondrial electron transport, ubiquinol to cytochrome c,","GO:0006122~mitochondrial electron transport, ubiquinol to cytochrome c,GO:0006334~nucleosome assembly,")
> unlist(str_extract_all(x, "(?<=~).*?(?=,(?:GO:\d+~|$))"))
[1] "peroxisome fission"                                         
[2] "mitochondrial electron transport, ubiquinol to cytochrome c"
[3] "mitochondrial electron transport, ubiquinol to cytochrome c"
[4] "nucleosome assembly"

Answer 2

在基础 R 中，你可以这样做：

sub(".*~",'', grep("~",t(read.csv(text = s, header = FALSE)), value = TRUE))
[1] "peroxisome fission"               "mitochondrial electron transport"
[3] "mitochondrial electron transport" "nucleosome assembly"

如何提取在 R 中一个字符之后和最后一次出现另一个字符之前发生的所有内容？

How to extract everything occurring after a character and before the last occurrence of another character in R?

regex

r

pattern-matching