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.
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;
Look at the plyr package for a general solution to
this type of problems:
http://cran.r-project.org/web/packages/plyr/index.html
and its introductory guide on the package home page:
http://had.co.nz/plyr/
HTH,
Tobias
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