Using grep to select strings contained in a list

Question

I have a dataframe:

id  <- c(1:5)
name <- c("blackdog","whitedog", "blackcat","whitecat","greyrabbit")
df <- data.frame(id,name)
df

I also have a list for selection:

select <- c("black","dog","grey")

So I want to return a dataframe containing: blackdog, blackcat,whitedog,greyrabbit

I have tried:

dfselect <-df[grep(select,df[,2]),]
dfselect

but this is only selecting the first element of the list.

I would be grateful for your help.

agstudy · Accepted Answer · 2014-05-31 08:45:29Z

2

No need to use a loop here:

df[grep(paste(select,collapse='|'),df$name),]

## id       name
## 1  1   blackdog
## 2  2   whitedog
## 3  3   blackcat
## 5  5 greyrabbit

answered May 31, 2014 at 8:45

agstudy

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1 Comment

ThatGuy Over a year ago

+1 - My first thought was to insert "|" in the list but I couldn't get it to work easily. What I missed was "collapse". Thanks!

ThatGuy · Accepted Answer · 2014-05-31 08:43:05Z

0

I think what you want to do is use the apply functions:

> df$name[unique(unlist(lapply(select, FUN=function(x) grep(x,df$name))))]
[1] blackdog   blackcat   whitedog   greyrabbit
Levels: blackcat blackdog greyrabbit whitecat whitedog

Is that what you were after?

answered May 31, 2014 at 8:43

ThatGuy

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