On Nov 5, 2009, at 7:53 PM, jimdare wrote:
I am create a new DF that summarizes the mean angle per treatment/
trial, of
the original DF (see below). I have had some success using:
(tapply(df$Angle, INDEX=interaction(df$State,
df$Trial), FUN=mean));
That's rather difficult to accept, since State is not a column name of
df.
however, this gives the answer as a list, which
means I would have to split the name to get the categories back. Does
anyone know a simple way to transform the Original DF into Summary DF?
Thanks in advance,
James
Original DF
df
Angle Trial Treatment
1 43.1297 1 C
2 62.3613 1 C
3 88.2767 2 C
4 75.2431 2 C
5 91.3668 3 C
6 61.2800 3 C
7 55.5575 1 U
8 69.4661 1 U
9 67.5512 2 U
10 95.5528 2 U
11 75.8689 3 U
12 66.9070 3 U
Summary DF
sdf
Angle Trial Treatment
1 52.7455 1 C
2 ... 2 C
snip
Try:
aggregate(df$Angle, list(df$Treatment,
df$Trial), sum)
Group.1 Group.2 x
1 C 1 105.4910
2 U 1 125.0236
3 C 2 163.5198
4 U 2 163.1040
5 C 3 152.6468
6 U 3 142.7759
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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