[R] how to do calculations in data matrices?

Sarah Goslee sarah.goslee at gmail.com
Sat Feb 13 18:50:06 CET 2010

Some places to start
and any of the good introductory guides to R available online.

For finding R material, it's vastly easier to use the custom search engine
at www.rseek.org than to wander aimlessly around google trying to
find things with "R" in them.

We'd be happy to give more specific answers if you need them,
especially if you do as the posting guide asks and provide
a reproducible example. (Not that you need one for this question,
since you did ask just for references.)


On Sat, Feb 13, 2010 at 12:39 PM, Zoppoli, Gabriele (NIH/NCI) [G]
<zoppolig at mail.nih.gov> wrote:
> Please give me just a reference where I can find something useful.
> In summary, I need to :
> - find the median of each row of a matrix
> - create a new matrix with each value in the first matrix divided by the median of its row
> - if a value "a" in the second matrix is < 1, I need to substitute it with 1/a
> I know that for some of you it must be overeasy, but I swear I googled for two hours with keywords "operations", "calculations", "data matrices", "data tables", and "CRAN", and I didn't find anything useful.
> Thank you all
> Gabriele Zoppoli, MD
> Ph.D. Fellow, Experimental and Clinical Oncology and Hematology, University of Genova, Genova, Italy
> Guest Researcher, LMP, NCI, NIH, Bethesda MD
> Work: 301-451-8575
> Mobile: 301-204-5642
> Email: zoppolig at mail.nih.gov
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Sarah Goslee

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