[R] rapply on a data.frame

From: Michael Hoffman <b3i4old02_at_sneakemail.com>
Date: Sun, 24 Feb 2008 20:44:48 +0000


Is it possible to get something like rapply for a data.frame? For example, if I do this:

 > x <- list(a=mtcars, b=mtcars)
 > str(rapply(x, nrow, classes="data.frame", how="replace")) List of 2
  $ a:List of 11
..$ mpg : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
..$ cyl : num [1:32] 6 6 4 6 8 6 8 4 4 6 ...
..$ disp: num [1:32] 160 160 108 258 360 ...
..$ hp : num [1:32] 110 110 93 110 175 105 245 62 95 123 ...
..$ drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
..$ wt : num [1:32] 2.62 2.88 2.32 3.21 3.44 ...
..$ qsec: num [1:32] 16.5 17.0 18.6 19.4 17.0 ...
..$ vs : num [1:32] 0 0 1 1 0 1 0 1 1 1 ...
..$ am : num [1:32] 1 1 1 0 0 0 0 0 0 0 ...
..$ gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ...
..$ carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ...
  $ b:List of 11
..$ mpg : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
..$ cyl : num [1:32] 6 6 4 6 8 6 8 4 4 6 ...
..$ disp: num [1:32] 160 160 108 258 360 ...
..$ hp : num [1:32] 110 110 93 110 175 105 245 62 95 123 ...
..$ drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
..$ wt : num [1:32] 2.62 2.88 2.32 3.21 3.44 ...
..$ qsec: num [1:32] 16.5 17.0 18.6 19.4 17.0 ...
..$ vs : num [1:32] 0 0 1 1 0 1 0 1 1 1 ...
..$ am : num [1:32] 1 1 1 0 0 0 0 0 0 0 ...
..$ gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ...
..$ carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ...

I was hoping to get something like list(a=11, b=11). I suspect this is because the data.frame is actually implemented as a list.



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