Hi On 19 Feb 2007 at 9:11, Duncan Murdoch wrote:
Date sent: Mon, 19 Feb 2007 09:11:52 -0500 From: Duncan Murdoch <[EMAIL PROTECTED]> To: Shubha Vishwanath Karanth <[EMAIL PROTECTED]> Copies to: r-help <R-help@stat.math.ethz.ch> Subject: Re: [R] categorical column to numeric column > On 2/19/2007 8:36 AM, Shubha Vishwanath Karanth wrote: > > Hi R, > > > > > > > > Let 'dd' be a data frame given as: > > > > > > > > dd=data.frame(aa=c("a","a","b","a","b","b"),bb=c(1,1,1,2,3,4)) > > > > > > > > Now I want to create a column 'g' such that if dd$aa=a then dd$g=1 > > else dd$g= -1 . > > > > > > > > So, I gave the below syntax: > > > > > > > > if((dd$aa)=="a") dd$g=1 else dd$g= -1 > > if() looks at just the first entry; it's designed for flow of control > rather than vectorized calculations. You want ifelse(): > > ifelse( dd$aa == "a", 1, -1) Another approach is to use the fact that logical vector can be interpreted as 1 and 0 vector (dd$a=="a")*2-1 HTH Petr > > Duncan Murdoch > > > > > > But I get the error message as: > > > > Warning message: > > > > the condition has length > 1 and only the first element will be used > > in: if ((dd$aa) == "a") dd$g = 1 else dd$g = -1 > > > > > > > > and dd= > > > > > > > >> dd > > > > aa bb g > > > > 1 a 1 1 > > > > 2 a 1 1 > > > > 3 b 1 1 > > > > 4 a 2 1 > > > > 5 b 3 1 > > > > 6 b 4 1 > > > >> > > > > > > > > Please let me know what is the error I am doing? > > > > > > > > > > > > > > > > > > > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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. Petr Pikal [EMAIL PROTECTED] ______________________________________________ R-help@stat.math.ethz.ch 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.