[R] The "median" function in R does not work properly.
Sundar Dorai-Raj
sundar.dorai-raj at PDF.COM
Thu Jun 24 22:38:19 CEST 2004
Alexi Zubiria wrote:
> Hi,
>
>
>
> 1.) The "median" function does not work well. Please refer to the data
> below (same data is attached as txt-delimited). This is what I try to
> do in R:
>
>
>
> median ( dataf [2:9] )
>
>
>
> I get warning: "needs numeric data"
>
>
>
> 2.) BUT if apply the median to a single vector:
>
>
>
> median ( dataf [,2]] )
>
>
>
> then it works:
>
>
>
>
>
> 3.) How come the "median" function does not let me take the median of
> all 8 vectors at once? Obviously, if I can perform the test on a single
> array, then it means I have numeric data because I do not get warning.
> Also, if I look at the "mode" for each array I get "numeric".
>
>
>
>
median *does* work properly and as documented:
Arguments:
x: a numeric vector containing the values whose median is to be
computed.
so you supplied a `list' or `data.frame' not a vector. I'm not sure what
you expected, but if you want to obtain the median of each column in
your matrix, then use ?apply:
apply(as.matrix(dataf), 2, median)
Or if you want to get the median of all vectors (a single number) then use
median(as.matrix(dataf))
I assume from your post you supplied a data.frame, however if dataf
really is a matrix (try data.class(dataf)) then median(dataf) will
accomplish the last line (at least on R-1.9.1 for win2000).
--sundar
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