On 30/06/10 20:46, Michael Lachmann wrote:
It took me some time to find this bug in my code. Is this a feature of
R? Am I doing something wrong?
> a=data.frame(x=1:10,y=1:10)
> b=data.frame(x=11:20,y=11:20)
> z=data.frame(1:10,11:20)
> a$z=z
You are (kind of) assigning *two* columns from the data frame "z" to the
name 'z' in "a" which is probably not going to work as you expect. R
tries to be clever which may or may not be a Good Thing. Try
a$z1 <- z[,1]
a$z2 <- z[,2]
or equivalent to keep the names straight.
As you have it, a$z is a data.frame, not a column, so you'd need a$z[,1]
to get the 1:10 back from the original assignment of z.
The default printing of a does not help: always check using str:
> str(a)
'data.frame': 10 obs. of 3 variables:
$ x: int 1 2 3 4 5 6 7 8 9 10
$ y: int 1 2 3 4 5 6 7 8 9 10
$ z:'data.frame': 10 obs. of 2 variables:
..$ X1.10 : int 1 2 3 4 5 6 7 8 9 10
..$ X11.20: int 11 12 13 14 15 16 17 18 19 20
Hope this helps a little.
Allan
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