On Dec 13, 2010, at 12:20 PM, Roy Shimizu wrote:
Hi! I'm just getting started with R (and with the analysis of large
datasets in general). I have several beginner-level questions whose
answers I have not been able to find, and was hoping one of you would
be kind enough to throw me a cluebrick or two.
I have a 6-dimensional numeric array (which I'll call myarray) that is
fully named. By this I mean that non-NULL dimnames are assigned to
all dimensions, and, furthermore, the dimensions themselves are named.
In fact, I created the dimnames attribute with an expression of the
form:
dimnames(myarray) - list(line=c(...), compound:name=c(...),
compound:concentration=c(...), time=c(...), replicate=c(...),
antibody:name=c(...))
...where the values passed for attributes line, compound:name, ..,
antibody:name are all vectors with mode character.
Question 1: I'd like to save this array in a file having an ASCII
(i.e. non-binary) format that can be easily read by R.
?dump
How can I
format this file so that not only the dimnames are specified, but also
the names of the dimensions (line, compound:name, ...,
antibody:name) themselves? I thought that the output of write.table
would give me a clue, but in fact this output does not mention the
dimension names at all.
Question 2: In fact, I don't think that write.table is the right
function to use in this case, because it seems to be designed for
dataframes rather than arrays. When write.table coerces myarray into
a data.frame, dimensions 2-6 get collapsed into one. Hence, when the
data is read back into R, it has the wrong dimensions. What's the
best way to convert a fully named array like myarray into a
data.frame, so as to preserve all the array's dimnames and dimension
names?
Question 3: I've come across several times the advice to the effect
that data.frames are usually the best choice of representation for
such data. In my case, however, I don't see what I would be gaining
by casting my array into a data.frame. In what kind of situation is
it advantageous to work with a data.frame rather than an array?
When you are going to do regression.
Thanks in advance!
David Winsemius, MD
West Hartford, CT
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