From: Philippe Grosjean <phgrosjean_at_sciviews.org>

Date: Sun 22 Jan 2006 - 22:00:17 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jan 22 22:25:21 2006

Date: Sun 22 Jan 2006 - 22:00:17 EST

Prof Brian Ripley wrote:

> 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
**> sapply(DF, median)
*

By the way, what is the preferred code for column-wise calculation on
*all numeric* data in a data frame?

> sapply(DF, median)

which considers the list and then simplifies the results down to a
vector or matrix,... or

> apply(DF, 2, median)

which first convert into a matrix and then do the calculation on it?
Best,

Philippe Grosjean

> 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)
**>>
**>>Best,
**>>
**>>Philippe Grosjean
**>>
**>>Liaw, Andy wrote:
**>>
**>>>apply(x, 1, median) should do it. If not, you need to explain why.
**>>>
**>>>Andy
**>>>
**>>>-----Original Message-----
**>>>From: Max Kauer
**>>>Sent: Friday, January 20, 2006 10:24 AM
**>>>To: r-help@stat.math.ethz.ch
**>>>Subject: [R] function for rowMedian?
**>>>
**>>>
**>>>Hi
**>>>is anybody aware of a function to calculate a the median for specified
**>>>columns in a dataframe or matrix - so analogous to rowMeans?
**>>>Thanks
**>>>Max
**>
**>
*

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jan 22 22:25:21 2006

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