Just in case some of x are negative (the desired median still exists, as long as the two middle values are non -ve), how about:
x <- runif(20, -1, 100) exp(median(log(pmax(0,x)))) It'll give -Inf if the two middle values are negative, when I guess we should get NaN, but I can't see a 1-line way to handle that! Keith J "Peter Ehlers" <ehl...@ucalgary.ca> wrote in message news:4d3468ef.5010...@ucalgary.ca... > I've been reminded by Prof. Brian Ripley that R's > log() function will indeed handle zeros appropriately. > > Apologies to S Ellison and Hadley Wickham. > > Peter Ehlers > > On 2011-01-17 06:55, Peter Ehlers wrote: >> On 2011-01-17 02:19, S Ellison wrote: >>> Will this do? >>> >>> x<- runif(20, 1, 100) >>> >>> exp( median( log( x) ) ) >>> >>> S Ellison >>> >>> >> That's what Hadley proposed, too. It's fine for >> your example, but there is potentially a small >> problem with this method: the data must be positive. >> Since it's not unusual to see data with some zeros, >> the log() would fail. >> >> Depending on what type of data I was going to use >> this modification of the median for, I would consider >> modifying the (quite short) median.default function, >> with appropriate additional data checks. >> >> Peter Ehlers >> >>> >>>>>> Skull Crossbones<witch.of.agne...@gmail.com> 15/01/2011 16:26>>> >>> Hi All, >>> >>> I need to calculate the median for even number of data points.However >>> instead of calculating >>> the arithmetic mean of the two middle values,I need to calculate their >>> geometric mean. >>> >>> Though I can code this in R, possibly in a few lines, but wondering if >>> there >>> is >>> already some built in function. >>> >>> Can somebody give a hint? >>> >>> Thanks in advance >>> > ______________________________________________ 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.
