[R] function for rowMedian?
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Jan 20 18:49:01 CET 2006
Interchange 1 and 2 (see ?apply: Andy was answering the subject line, not
that in the body).
However, Max asked also for column medians of a data frame, for which use
I didn't understand the question, and it seems I was not alone :)
On Fri, 20 Jan 2006, Philippe Grosjean wrote:
> Note that there is a confusion here: 1st dimension is row, 2nd dimension
> is column for matrix & data.frame.
And the dim arg to apply is the one you want the answer to have.
A <- matrix(runif(6), 2, 3)
apply(A, 1, median) # row medians
apply(A, 2, median) # col medians
> So, if the question is about "rowMedian", you have:
> > rowMedian <- function(x, na.rm = FALSE)
> > apply(x, 2, median, na.rm = na.rm)
> Now, you ask for the "median for specified columns", which should be as
> Andy proposes you, or, if you really want a colMedian function:
> > colMedian <- function(x, na.rm = FALSE)
> > apply(x, 1, median, na.rm = na.rm)
> Philippe Grosjean
> Liaw, Andy wrote:
>> apply(x, 1, median) should do it. If not, you need to explain why.
>> -----Original Message-----
>> From: Max Kauer
>> Sent: Friday, January 20, 2006 10:24 AM
>> To: r-help at stat.math.ethz.ch
>> Subject: [R] function for rowMedian?
>> is anybody aware of a function to calculate a the median for specified
>> columns in a dataframe or matrix - so analogous to rowMeans?
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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