Hi:

Here's a *reproducible* example:

> a <- data.frame(w = rnorm(10), x = rnorm(10), y = rnorm(10), z =
rnorm(10))
> b <- data.frame(w = rnorm(20), x = rnorm(20), x2 = rnorm(20), x3 =
rnorm(20))
> commonCols <- intersect(names(a), names(b))
> commonCols
[1] "w" "x"
> rbind(a[commonCols], b[commonCols])

HTH,
Dennis

On Thu, Jul 29, 2010 at 3:53 AM, pdb <philb@philbrierley.com> wrote:

>
> I have 2 data frames (A & B) with some common column names.
>
> A has 10 rows.
> B has 20 rows.
>
> How do I combine them so I end up with a data frame with 30 rows that only
> contains the common columns.
>
> I was trying 'merge' (Merge two data frames by common columns .....etc. )
> but that is not giving me what I expect...
>
> > a <- iris
> > b <- iris
> >
> > c <-merge(a,b)
> >
> > NROW(a)
> [1] 150
> > NROW(c)
> [1] 152
>
> Why is there only 152 rows and not 300?
>
>
>
> --
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>
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