R Identifing text string within column of dataframe

Question

One column of my data frame has words and phrases. I am trying to create a dummy variable for those fields within this column that have specific strings of text anywhere within.

For example:

kite
cars
box kites
model cars
i like kites that fly

cars of the world

 myvector<-c("kite","cars","box kites","model cars","i like kites that fly",
 "cars of the world")

I would want to identify all the fields with the string "kite"

I've tried a few things such as any(), which() and %in% but nothing has worked so far.

Any help greatly appreciated

Luciano Selzer · Accepted Answer · 2012-09-13 15:31:00Z

33

You didn't provided any reproducible example. But your answer will be grepl.

grepl("kite", df$words)

It will return a logical vector if the word is in the row.

If you want to match multiple words use logical or | inside the string to match

grepl("kite|cars|box kites", df$words)

edited Sep 13, 2012 at 15:31

answered Sep 13, 2012 at 15:11

Luciano Selzer

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4 Comments

Will Phillips Over a year ago

cool, this works really well. If I had 2 or more words would I just repeat this with another grepl()? I tried searching 2 words with grepl(c("word1","word2"),df$words) R didn't like that. I also tried it with grepl("word1"|"word2",df$words) and grepl("word1"||"word2",df$words) but no luck. I can do multiple grepl()'s. I don't have that many words but I thought I would ask.

Will Phillips Over a year ago

create 1 dummy variable (1 or 0) but there are a few words to search on that would get a "1". I can do grepl() for each word separately, sum the resulting vectors and ifelse a final vector if the sum is 0 then 0 else 1. Though if it could work in a single grepl() it's more efficient.

Will Phillips Over a year ago

oh, the | is inside the quotes. awesome! Thanks

mikey Over a year ago

@willPhillips If you want to use a vector you could use grepl(paste0(c("word1","word2"), collapse='|'), df$words)

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