Hello John,
Thank you for hosting the R-User meeting on Tuesday. I found it interesting.
However, I was a bit disappointed with the turn out. I thought that there
would be more people with an interest in R here. You can count of me as an
active member from now on.
In the fall, at one of the meetings, I would be happy to give a 20 minute
talk on "Spatial classes and their use in R". Also I have done a fair bit of
work with the packages 'plyr' and 'data.table' for the
manipulation/massaging of data in R (if anybody would be interested in
learning about these things I could give a short presentation?).
Also is there a way I can communicated with any of the people attending the
meeting by e-mail? Did anybody collect the e-mail addresses of the people
there?
Again thanks for your work in organizing things. Have a productive "Google
Summer of Code".
Regards,
John Lewis

On Thu, May 26, 2011 at 6:00 AM, <r-ug-ottawa-request@r-project.org> wrote:

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>   1. Report on May 24 meeting (Prof. John C Nash)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 25 May 2011 18:23:45 -0400
> From: "Prof. John C Nash" <nashjc@uottawa.ca>
> To: r-ug-ottawa@r-project.org
> Subject: [OGRUG] Report on May 24 meeting
> Message-ID: <4DDD8171.8050007@uottawa.ca>
> Content-Type: text/plain; charset=ISO-8859-1
>
> While we had only a small group (8) at the meeting, discussion was lively
> and some minor
> problems were resolved.
>
> There was quite a lot of interest in the projects R is mentoring for the
> Google Summer of
> Code. This year we have 15. There is a brief outline of the projects linked
> directly from
> the main www.r-project.org page.
>
> There were two pre-announced R coding questions.
>
> David Joubert had an SPSS data file that he wanted to bring into R to
> either use in
> creating a 5 dimensional frequency array or else convert to a numerical
> (rather than
> character) raw data file of binary information on 5 symptom variables for
> 500 cases.
>
> The foreign package can read the data into a data frame, but the binary
> variables are of
> class factor. After the meeting a bit of playing showed that as.numeric()
> will convert
> these to numbers (1, 2) and write.csv will write them in a form that is
> easily changed in
> a spreadsheet to the form needed by some specialized software. It should in
> fact be
> possible to avoid the last step by appropriate parameters to write.csv.
>
> John Nash illustrated a concern for those working on optimization,
> differential equations
> or quadrature when it is desired to record every function evaluation of a
> multivariate
> function e.g., the objective in optimization. The issue is to avoid passing
> such
> information through the optimizer, which may be compiled code and difficult
> to access.
> While it should be possible to use environments, there seemed to be a
> general view that
> this tended to be more tricky than anyone liked. However, we were able in a
> small example
> to set a global object f.save to NULL, then use rbind inside the function
> to append the
> vector c(f, x_vector). It was agreed this was NOT a good idea for inclusion
> in a package,
> but likely the most straightforward tool for experimentation.
>
> This lead to a discussion of the merits of using return() to end R
> functions, and a brief
> attempt to test the speed of use of return(x) versus just ending with the
> evaluation of x
> using the microbenchmark package. This was inconclusive for the simple
> example tried.
>
> We hope to have a similar event in the Autumn with more problems
> pre-announced.
>
> John Nash
>
>
>
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> End of R-UG-Ottawa Digest, Vol 15, Issue 3
> ******************************************
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