On 9/15/2009 4:24 PM, ivo welch wrote:
hi david---no, this time I actually know what I was asking ( ;-) ). I do
need speed computed on many data sets, each of which is created by a "by"
statement. so, no iterative programming on my side.
thanks, hadley for the pointer to .row_names_info() in lieu of dim() or
nrows(). I don't seem to understand the second (type) argument, despite
reading the docs, but all of them are giving the same answer in my data
frames. so, I guess I will stick to "2" for the time being.
One note: if you're worried about speed, it almost always makes sense
to use matrices rather than dataframes. If you've got mixed types this
is tedious and error-prone (each type needs to be in a separate matrix),
but if your data is all numeric, it's very simple, and will make things
a lot faster.
Duncan Murdoch
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