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.

regards,

/iaw

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