Calculate median from counts and values

On 5/3/05, David Finlayson <david.p.finlayson at gmail.com> wrote:

I am tangled with a syntax question. I want to calculate basic statistics
for a large dataset provided in weights and values and I can't figure out
an elegant way to expand the data.

For example here are the counts:

counts

   n4 n3 n2 n1 p0 p1 p2 p3  p4
1   0  0  0  1  1  3 16 55  24
2   0  0  0  0  2  8 28 47  15
3   1 17 17 13  4  5 12 24   8
...

and the values:

values

     n4 n3 n2 n1 p0  p1   p2    p3     p4
[1,] 16  8  4  2  1 0.5 0.25 0.125 0.0625

What I want for each row is something like this (shown for row 1):

c( rep(16, 0), rep(8, 0), rep(4, 0), rep(2, 1), rep(1, 1), rep(0.5, 3),
rep(0.25, 16), rep(0.125, 55), rep(0.0625, 24))

I am sure that this is a one-liner for an R-master, but I can't figure it
out without a set of nested for loops iterating over each row in counts.

Is there supposed to be one row of values that apply to all
rows of counts or is there to be different rows of values for
different rows of counts?  Also in your example row 3 has
a different total than 1 or 2.  Is that right?

At any rate, I will assume that there is only one row of
values and many rows of counts and that its not necessarily
true that counts sum to the same number in each row.
Then noting that  c(rep(4,1), rep(5,2), rep(6,3)) is the same
as rep(4:6, 1:3) is the same as, we have:

lapply(as.data.frame(t(counts)), rep, x = unlist(values))