grep多个模式并计算字符串r中有多少个模式

我有一个问题，关于计算一个字符串中有多少匹配的模式

比如说,， 我有一个数据帧'

index  string
1      'I have first and second'
2      'I have first'
3      'I have second and first and third'

和一个叫做toMatch的匹配模式向量

toMatch <-  c('first', 'second', 'third')

现在我只能用

grepl(paste(toMatch, collapse = "|"), s$string) 

它将返回哪个字符串匹配toMatch中的任何元素，但我如何知道匹配了多少元素

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任何帮助都将不胜感激！提前谢谢

另一种可能更快：

data.frame(string=s$string, count=rowSums(sapply(toMatch, function(x) grepl(x, s$string))))

您的数据：

dat <- read.table(text="index  string
1      'I have first and second'
2      'I have first'
3      'I have second and first and third'", header=TRUE)

toMatch <-  c('first', 'second', 'third')

dat
dat <- read.table(text="index  string
1      'I have first and second'
2      'I have first'
3      'I have second and first and third'", header=TRUE)

toMatch <-  c('first', 'second', 'third')

library(stringi)
dat$count <- stri_count_regex(dat$string, paste(toMatch, collapse="|"))
dat

##   index                            string count
## 1     1           I have first and second     2
## 2     2                      I have first     1
## 3     3 I have second and first and third     3