On Sep 28, 2009, at 11:39 AM, baxterj wrote:
I have a simple 1 way anova coded like
summary(ANOVA1way <- aov(Value ~ WellID, data = welldata))
How can I use the BY function to do this ANOVA for each group using
another
variable in the dataset?? I tried coding it like this, but it
doesn't seem
to work.
Since you have not offered a reproducible example, we are left to
choose our own. Checking the help page for "by" we see that a problem
extremely similar to yours is already solved. I choose not to attach()
the data for well-understood reasons:
anova.LMH <- by(warpbreaks, warpbreaks$tension, function(x) aov(breaks
~ wool, data=x) )
summary(ANOVA1way <- by(welldata, Analyte, function(x) aov(Value ~
WellID,
data = welldata)))
In SAS I would code it like this:
Proc sort data=welldata; by analyte; run;
Proc glm data=welldata;
by analyte;
class wellid;
model value = wellid;
run;
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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