counts for grouped data
On Thu, 4 Sep 2003, Paul Green wrote:
How does one get counts for grouped data
from ungrouped data. For example, how can
I get
X1 X2 Count
1 1 1
1 2 2
2 1 1
2 2 1
from
X1 X2
A A
A B
B B
A B
B A
One possibility is
df
X1 X2 1 A A 2 A B 3 B B 4 A B 5 B A
aggregate(rep(1,nrow(df)), df, NROW)
X1 X2 x 1 A A 1 2 B A 1 3 A B 2 4 B B 1 -thomas