如何将grep / regex命令列表传递给R函数

I have a list of roughly 50 somewhat complicated grepl commands strings that I would like to pass to a function in R. I am using these functions to subset a dataframe. Here is an example of 2 of the commands:

我有一个大约50个有点复杂的grepl命令字符串的列表，我想传递给R中的函数。我使用这些函数来子集数据帧。以下是2个命令的示例：

t <- subDF[grepl("(extreme|abnormal|unseasonably|unusually|record|excessive) (heat|warm|high temp)",subDF$EVTYPE),]

t <- subDF[grepl("fl(oo)?d",subDF$EVTYPE) & !grepl("flash",subDF$EVTYPE) & !grepl("(tidal|beach|(c(oa)?sta?l))(/tidal)? ?(flood)",subDF$EVTYPE),]

So, in this example I would like to pass pass these 2 grepl commands to a function that will do this subsetting on dataframe subDF (plus pass the other 48 or so).

因此，在这个例子中，我希望将这两个grepl命令传递给一个函数，该函数将在dataframe subDF上执行此子集化（另外传递其他48个左右）。

Any elegant way to do this?

有什么优雅的方法吗？

2 个解决方案

#1

Here's an example that uses quote to create two unevaluated grepl calls. They are then evaluated in an sapply call with eval.

这是一个使用quote创建两个未评估的grepl调用的示例。然后使用eval在一个sapply调用中评估它们。

> fruits <- c("one apple", "two pears", "three bananas")
> QQ <- list(q1 = quote(grepl("(one)|(apple)", fruits)),
             q2 = quote(grepl("apple", fruits) | grepl("bananas|one", fruits)))
> sapply(QQ, function(x) fruits[eval(x)])
#$q1
#[1] "one apple"
# 
#$q2
#[1] "one apple"     "three bananas"

A look at QQ

一看QQ

#$q1
#grepl("(one)|(apple)", fruits)
#
#$q2
#grepl("apple", fruits) | grepl("bananas|one", fruits)

Something else that is useful is

其他有用的东西是

> as.list(quote(grepl("one|apple", fruits)))
# [[1]]
# grepl
#
# [[2]]
# [1] "one|apple"
# 
# [[3]]
# fruits

With this, you can replace the regular expression (or call or x) in every iteration by way of [[ indexing.

有了这个，你可以通过[[indexing]的方式在每次迭代中替换正则表达式（或call或x）。

#2

It looks like you're after Reduce. Using the iris dataset as an example:

看起来你在Reduce之后。以虹膜数据集为例：

mygrep <- function(x, df) df[grepl(x, df$Species), ]
pat <- c("setosa", "(setosa|virginica)")

Reduce(mygrep, pat, iris, right=TRUE)

#1