[R] different interface to by (tapply)?

[ivo welch]

dear R experts:

has someone written a function that returns the results of by() as a
data frame?   of course, this can work only if the output of the
function that is an argument to by() is a numerical vector.
presumably, what is now names(byobject) would become a column in the
data frame, and the by object's list elements would become columns.
it's a little bit like flattening the by() output object (so that the
name of the list item and its contents become the same row), and
having the right names for the columns.  I don't know how to do this
quickly in the R way.  (Doing it slowly, e.g., with a for loop over
the list of vectors, is easy, but would not make a nice function for
me to use often.)

for example, lets say my by() output is currently

by( indf, indf$charid, function(x) c(m=mean(x), s=sd(x)) )

$`A`
[1] 2 3
$`B`
[2] 4 5

then the revised by() would instead produce

charid  m  s
A          2  3
B          4  5

working with data frames is often more intuitive than working with the
output of by().  the R wizards are probably chuckling now about how
easy this is...

regards,

/iaw

----
Ivo Welch (ivo.welch at brown.edu, ivo.welch at gmail.com)