[R] median by geometric mean

Peter Ehlers ehlers at ucalgary.ca
Mon Jan 17 15:55:39 CET 2011


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.agnessi at 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
>
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