I have a straightforward application of ddply() and summarize():
ddply(MyFrame, .(Treatment, Week), summarize, MeanValue=mean(MyVar))
This works just fine:
Treatment Week MeanValue
1 MyDrug BASELINE 5.91
2 MyDrug WEEK 1 4.68
3 MyDrug WEEK 2 4.08
4 MyDrug WEEK 3 3.67
5 MyDrug WEEK 4 2.96
6 MyDrug WEEK 5 2.57
7 MyDrug WEEK 6 2.50
8 Placebo BASELINE 8.58
9 Placebo WEEK 1 8.25
...
But I want to specify the variable (MyVar) as a character string:
ddply(MyFrame, .(Treatment, Week), summarize, MeanValue=mean("MyVar"))
(Actually, the character string "MyVar" will be selected from a vector of
character strings.)
The code above produces no joy:
Treatment Week MeanValue
1 MyDrug BASELINE NA
2 MyDrug WEEK 1 NA
3 MyDrug WEEK 2 NA
4 MyDrug WEEK 3 NA
...
I tried a few things, including:
as.name("MyVar")
as.quoted("MyVar")
... but they all produced the name results: NAs
I'm obviously thrashing around in the dark! Any advice would be greatly
appreciated.
-John
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