[R] merge problem
Sundar Dorai-Raj
sundar.dorai-raj at pdf.com
Thu Sep 25 17:52:26 CEST 2003
Hi all,
I just discovered a problem when merging two data.frames which don't
have any columns in common and when one (or both) of the data.frames is
a single column. E.g.
x <- data.frame(x = 1:5, y = letters[1:5])
y <- data.frame(z = 1:2)
z <- merge(x, y)
The result z is as expected, but the resulting names of z are not right.
I've tracked it down to following the line in merge.data.frame:
if (l.b == 0) {
ij <- expand.grid(1:nx, 1:ny)
res <- cbind(x[ij[, 1], ], y[ij[, 2], ]) # <--- HERE
}
Changing this line to:
res <- cbind(x[ij[, 1], , drop = FALSE], y[ij[, 2], , drop = FALSE])
resolves the problem.
S-PLUS 6.1 does not have this problem.
Hope this is helpful to others.
-sundar
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