[R] Getting frustrated with RMySQL
r.ted.byers at gmail.com
Tue Oct 14 21:33:13 CEST 2008
Getting the basic stuff to work is trivially simple. I can connect, and, for
example, get everything in any given table.
What I have yet to find is how to deal with parameterized queries or how to
do a simple insert (but not of a value known at the time the script is
written - I ultimately want to put my script into a scheduled task, so the
analysis can be repeated on updated data either daily or weekly).
Using "INSERT INTO myTable (a) VALUES (1)" is simple enough, but what if I
want to insert a sample number (using, e.g. WEEK(sample_date) as a sample
identifier) along with the rate parameter estimated using fitdistr to fit an
exponential distribution to a dataset, along with its sd? If I were using
Perl or Java, I'd set up the query similar to "INSERT INTO myTable (a,b,c)
VALUES (?,?,?)", and then use function calls to set each of the query
parameters. I am having an aweful time finding the corresponding functions
And for the data, the simplest, and most efficient, way to get the data is
to use a statement like:
SELECT a,b,c FROM myTable GROUP BY g_id, WEEK(sdate);
The data is in MySQL, and my analysis needs to be applied independantly to
each group obtained from a query like this. It appears I can't use a data
frame since none of the samples are of the same size (lets say the
probability of the samples being the same size in indistinguishable from 0).
Is it possible to put the resultset from such a query into a list of vectors
that I can iterate over, passing each vector to fitdistr in turn? If so,
I know I can get this using Perl (by getting each sample individually and
writing it to a file, then having R read the file, do the analysis and write
the output to another file, and then have Perl parse the output file to
insert the parameter estimates I need into the appropriate table), but that
Is it possible to do all I need with R working directly with MySQL? If so,
can someone fill in the apparent gaps left in the RMySQL documentation?
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