match part of string in R

Question

I'm stuck with something that usually is pretty easily in other programming languages.

I want to test whether a string is inside another one in R. For example I tried:

match("Diagnosi Prenatale,Esercizio Fisico", "Diagnosi Prenatale")
pmatch("Diagnosi Prenatale,Esercizio Fisico", "Diagnosi Prenatale")
grep("Diagnosi Prenatale,Esercizio Fisico", "Diagnosi Prenatale")

And none worked. To make it work I should fist split the first string with strsplit and extract the first element.

NOTE: I'd like to do this on a vector of strings to receive a yes/no vector, so in the function I wrote should go a vector not a single string. But of course if the single string doesn't work, image a full vector of them...

Any ideas?

Some quick notes: (1) you wouldn't use match or pmatch for this task - these are for matching in a list. (2) you're using grep incorrectly - the pattern is the first argument and the text is the second. — rrs
– rrs, Commented May 30, 2014 at 14:50

talat · Accepted Answer · 2014-05-30 14:44:00Z

4

Try grepl

grepl("Diagnosi Prenatale","Diagnosi Prenatale,Esercizio Fisico" )
[1] TRUE

You can also do this with character vectors, for example:

x <- c("Diagnosi Prenatale,Esercizio Fisico", "Diagnosi Prenatale")
grepl("Diagnosi Prenatale",x)
#[1] TRUE TRUE

answered May 30, 2014 at 14:44

talat

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1 Comment

rrs Over a year ago

Good answer. I would note that the OP used grep incorrectly which is why his code didn't work. I'm often throw off by the fact that pattern is the first argument.

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