To find the proportion of "yes"s in pp you can use mean(pp == "yes") and avoid the conversion of a factor to integer (and subtracting 1). The above works for character and factor pp.
Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of Francesco Sarracino > Sent: Wednesday, January 23, 2013 1:59 AM > To: D. Rizopoulos > Cc: R help > Subject: Re: [R] problems with coercing a factor to be numeric > > Thanks, > this works! but I am surprised that R has such a strange behavior and that > there is no way to control it. > BTW, also as.integer(pp)-1 works! > Still, it doesn't look to me as a first best. > At any rate, thanks a lot for your help. > f. > > > On 23 January 2013 10:53, D. Rizopoulos <d.rizopou...@erasmusmc.nl> wrote: > > > check also > > > > pp <- rep(0:1, 10) > > pp <- factor(pp, levels=(0:1), labels=c("no","yes")) > > > > unclass(pp) > > unclass(pp) - 1 > > > > > > Best, > > Dimitris > > > > > > On 1/23/2013 10:48 AM, Francesco Sarracino wrote: > > > Dear Dimitris, > > > > > > thanks for your quick reply. I've tried the solutions proposed in 7.10 > > > How do I convert factors to numeric? > > > > > > as.numeric(as.character(pp)) > > > and > > > as.numeric(levels(pp))[as.integer(pp)] > > > > > > However, whatever I do, I get "Warning message: NAs introduced by > > coercion" > > > and the output is a vector of NA. > > > > > > Any ideas? > > > f. > > > > > > > > > > > > On 23 January 2013 10:39, D. Rizopoulos <d.rizopou...@erasmusmc.nl > > > <mailto:d.rizopou...@erasmusmc.nl>> wrote: > > > > > > Check R FAQ 7.10: How do I convert factors to numeric? > > > > > > > > > I hope it helps. > > > > > > Best, > > > Dimitris > > > > > > > > > On 1/23/2013 10:33 AM, Francesco Sarracino wrote: > > > > Dear R listers, > > > > > > > > I am trying to compute the mean of a dummy variable that is > > > encoded as a > > > > factor. However, even though the levels of my factor are 0 - 1, > > > when I > > > > compute the mean (after coercing the factor to be > > > > numeric), R changes 0 into 1 and 1 into yes, thus altering my > > > expected > > > > result. > > > > > > > > Please, consider the following working example: > > > > pp <- rep(0:1, 10) > > > > pp <- factor(pp, levels=(0:1), labels=c("no","yes")) > > > > mean(pp) #this won't work because the argument is not numeric or > > > logical > > > > mean(as.integer(pp)) # this computes the average, but not on the > > > range 0-1, > > > > but 1-2. Indeed, the result is 1.5 and not 0.5 as expected. > > > > > > > > What am I doing wrong? > > > > Thanks in advance for your kind support, > > > > f. > > > > > > > > > > > > > > -- > > > Dimitris Rizopoulos > > > Assistant Professor > > > Department of Biostatistics > > > Erasmus University Medical Center > > > > > > Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands > > > Tel: +31/(0)10/7043478 <tel:%2B31%2F%280%2910%2F7043478> > > > Fax: +31/(0)10/7043014 <tel:%2B31%2F%280%2910%2F7043014> > > > Web: http://www.erasmusmc.nl/biostatistiek/ > > > > > > > > > > > > > > > -- > > > Francesco Sarracino, Ph.D. > > > https://sites.google.com/site/fsarracino/ > > > > -- > > Dimitris Rizopoulos > > Assistant Professor > > Department of Biostatistics > > Erasmus University Medical Center > > > > Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands > > Tel: +31/(0)10/7043478 > > Fax: +31/(0)10/7043014 > > Web: http://www.erasmusmc.nl/biostatistiek/ > > > > > > -- > Francesco Sarracino, Ph.D. > https://sites.google.com/site/fsarracino/ > > [[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.
