Question

This should be simple but for some reason I’m stuck. I have data that looks like

A <- data.frame(x=rnorm(10), y=rnorm(10), z=rnorm(1))
B <- data.frame(x=rnorm(10), y=rnorm(10), z=rnorm(1))
C <- data.frame(x=rnorm(10), y=rnorm(10), z=rnorm(1))

method1 <- list(A=A,B=B,C=C)
method2 <- list(A=A,B=B,C=C)

biglist <- list(method1, method2)

And I’d like to reformat the data to look like

x y z   dataset  method
- - -   ---       -----
1 1 1    A          1
1 0 2    A          1
1 0 3    A          1
1 1 3    A          1
1 1 1    B          1
1 0 2    B          1
1 0 3    B          1
1 1 3    B          1
1 1 1    C          1
1 0 2    C          1
1 0 3    C          1
1 1 3    C          1
1 1 1    A          2
1 0 2    A          2
1 0 3    A          2
1 1 3    A          2
1 1 1    B          2
1 0 2    B          2
...

melt doesn’t quite do what I want because it collapses my x/y/z variable headings.

Answer 1

Your data.frames should have a primary key,
e.g., an identifier column, or a column with unique values —
otherwise, you will end up with the x, y, z
coordinates of a point in several unrelated rows.
I will assume that x is such a column.

You may also have to call dcast after melt,
if the resulting data.frame is too vertical.

library(reshape2)
d <- melt(biglist, id.vars="x")
d <- dcast( d, L1 + L2 + x ~ variable )