On Oct 21, 2011, at 1:04 PM, Rich Shepard wrote:
On Fri, 21 Oct 2011, Weidong Gu wrote:
No easy way out with missing data problems, all imputations are
based on
some strong and untestable assumptions.
Thanks for the insights.
Let me rephrase my question in a way that should work: is there a
way to
subset my comprehensive data frame ('chemdata') to select only those
rows
that have values for two different parameters (i.e., in the same
column)?
The last part ("in the same column") does not make sense, since I was
interpreting the term "parameter" to mean a value in a particular
column. Assuming these are R NA's then logical indexing:
with( chemdata, chemdata[!is.na(param1) & !is.na(param2) , ])
If you are talking about extracting different text features from a
single character field then look at `grepl`.
patt1 <- "S2" # any appearance of that string
patt2 <- "E5" # any appearance of that string
with( chemdata, chemdata[ grepl(patt1, param1) & grepl(patt2,
param1) , ])
I suspect not. But, I can select from the database table on those
criteria
and read in a new R data frame.
That to should b possible. Specifics are sorely lacking at this point,
however.
Rich
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David Winsemius, MD
West Hartford, CT
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