>From ?regex "(do remember that backslashes need to be doubled when entering R character strings, e.g. from the keyboard)."
> lines[grep("^([a-z]+) +\\1 +[a-z]+ [0-9]",lines)] [1] "night night at 8" ------------------------------------- David L Carlson Department of Anthropology Texas A&M University College Station, TX 77840-4352 -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Lopez, Dan Sent: Tuesday, October 29, 2013 12:13 PM To: R help (r-help@r-project.org) Subject: [R] Regular Expression returning unexpected results Hi, So I just took an intro to R programming class and one of the lectures was on Regular Expressions. I've been playing around with various R functions that use Regular Expressions. But this has me stumped. This was part of a quiz and I got it right through understanding the syntax. But when I try to run the thing it returns 'integer(0)'. Can you please tell me what I am doing wrong? #I copied and pasted this: going up and up and up night night at 8 bye bye from up high heading, heading by 9 #THEN lines<-readLines("clipboard") #This is what it looks like in R lines [1] "going up and up and up" [2] "night night at 8" [3] "bye bye from up high" [4] "heading, heading by 9" #THIS IS WHAT IS NOT WORKING THE WAY I THOUGHT. I was expecting it to return 2. # "night night at 8" follows the pattern: Begins with a word then has at least one space then the same word then has at least one space then a word then a space then a single digit number. grep("^([a-z]+) +\1 +[a-z]+ [0-9]",lines) integer(0) #But simple examples DO work grep("[Hh]",lines) [1] 2 3 4 grep('[0-9]',lines) [1] 2 4 [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.