regex - 使用正则表达式从字符串中提取

Question

我有一个字符串:

s <- "test.test AS field1, ablh.blah AS field2, faslk.lsdf AS field3"

我想转换为:

"field1, field2, field3"

我知道正则表达式 (\w+)(?:,|$)将提取我想要的字符串('field1' 等)，但我不知道如何使用 gsub 提取它.

Answer 1

## Preparation
s <- "test.test AS field1, ablh.blah AS field2, faslk.lsdf AS field3"
pat <- "(\\w+)(?:,|$)"  ## Note the doubly-escaped \\w

## Use the powerful gregexpr/regmatches one-two punch
m <- gregexpr(pat, s)
paste(regmatches(s, m)[[1]], collapse=" ")
# [1] "field1, field2, field3"