M. Siwik M. Siwik - 1 year ago 81
R Question

How to match regular expression exacly in R and pull out pattern

I want to get pattern from my vector of strings

string <- c(
"P10000101 - Przychody netto ze sprzedazy produktów" ,
"P10000102_PL - Przychody nettozy uslug",
"P1000010201_PL - Handlowych, marketingowych, szkoleniowych",
"P100001020101 - - Handlowych,, szkoleniowych - refaktury",
"- Handlowych, marketingowych,P100001020102, - pozostale"

As result i want to get exact match of regular expression

result <- c(

I tried with this
pattern = "([PLA]\\d+)"
and diffrent combination of
value = T, fixed = T, perl = T.

grep(x = string, pattern = "([PLA]\\d+(_PL)?)", fixed = T)

Answer Source

We can try with str_extract

str_extract(string, "P\\d+(_[A-Z]+)*")
#[1] "P10000101"      "P10000102_PL"   "P1000010201_PL" "P100001020101"  "P100001020102" 

grep is for finding whether the match pattern is present in a particular string or not. For extraction, either use sub or gregexpr/regmatches or str_extract

Using the base R (regexpr/regmatches)

regmatches(string, regexpr("P\\d+(_[A-Z]+)*", string))
#[1] "P10000101"      "P10000102_PL"   "P1000010201_PL" "P100001020101"  "P100001020102" 

Basically, the pattern to match is P followed by one more numbers (\\d+) followed by greedy (*) match of _ and one or more upper case letters.

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