Dear Steven, Beyond ?regex, the Wikipedia article on regular expressions <https://en.wikipedia.org/wiki/Regular_expression> is quite helpful and not too long. I hope this helps, John On 2022-07-10 9:43 p.m., Steven T. Yen wrote:> Thanks Jeff. It works. If there is a good reference I should read > (besides ? grep) I's be glad to have it. > > On 7/11/2022 9:30 AM, Jeff Newmiller wrote: >> grep( "^(z|x)\\.", jj, value = TRUE ) >> >> or >> >> grep( r"(^(z|x)\.)", jj, value = TRUE ) >> >> >> On July 10, 2022 6:08:45 PM PDT, "Steven T. Yen" <styen at ntu.edu.tw> >> wrote: >>> Dear, Below, jj contains character strings starting with ?z.? and >>> ?x.?. I want to grep all that contain either ?z.? or ?x.?. I had to >>> grep ?z.? and ?x.? separately and then tack the result together. Is >>> there a convenient grep option that would grep strings with either >>> ?z.? or ?x.?. Thank you! >>> >>>> jj<-names(v$est); jj >>> ??[1] "z.one"???? "z.liberal" "z.conserv" "z.dem"???? "z.rep" >>> "z.realinc" >>> ??[7] "x.one"???? "x.liberal" "x.conserv" "x.dem"???? "x.rep" >>> "x.realinc" >>> [13] "mu1_1"???? "mu2_1"???? "rho" >>>> j1<-grep("z.",jj,value=TRUE); j1 >>> [1] "z.one"???? "z.liberal" "z.conserv" "z.dem"???? "z.rep" "z.realinc" >>>> j2<-grep("x.",jj,value=TRUE); j2 >>> [1] "x.one"???? "x.liberal" "x.conserv" "x.dem"???? "x.rep" "x.realinc" >>>> j<-c(j1,j2); j >>> ??[1] "z.one"???? "z.liberal" "z.conserv" "z.dem"???? "z.rep" >>> "z.realinc" >>> ??[7] "x.one"???? "x.liberal" "x.conserv" "x.dem"???? "x.rep" >>> "x.realinc" >>> >>> ______________________________________________ >>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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.-- John Fox, Professor Emeritus McMaster University Hamilton, Ontario, Canada web: https://socialsciences.mcmaster.ca/jfox/