How to negate a particular pattern in string using regex?

Asked Feb 23 '18 at 01:07

Active Feb 23 '18 at 01:27

Viewed 160 times

I have a string where i want to extract a particular pattern only.

x<-c("N4553","3805U","celeron N4553","applheddd")
gregextract <- gregexpr('\\bceleron\\b|\\bN[0-9]+\\b',x,perl=TRUE)
size1<- regmatches(x,gregextract,invert = FALSE)

It extracts both the occurrences of N, I need only celeron to be extracted(where a combination of celeron N4533 occurs) without N4533. I cannot remove N[0-9] pattern as it is used of other occurrences in different rows.

edited Feb 23 '18 at 01:16

Ronak Shah

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asked Feb 23 '18 at 01:07

Richie

There is nothing extracted so far on my end – Onyambu Feb 23 '18 at 01:14
@Onyambu - works for me - look at `size1` output – thelatemail Feb 23 '18 at 01:15
ohh I see what you mean. use `regexpr` instead of `gregexpr` – Onyambu Feb 23 '18 at 01:19
try looking up regex capture groups in r. Seems to be plenty out there – Kind Stranger Feb 23 '18 at 02:29
Do you want to get the whole character string if there are 2 whole words, `celeron` and `N+digits` regardless of order? Try https://ideone.com/iTAFYY – Wiktor Stribiżew Feb 23 '18 at 07:26
@WiktorStribiżew- If "Celeron N4553" occurs , i need only the celeron and restrict the regex not to extract N4553 from "Celeron N4553". However i have individual occurrences of "N4553" where it should extract "N4553" . – Richie Feb 27 '18 at 03:30

How to negate a particular pattern in string using regex?

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