[R] Running an ANOVA with a BY

baxterj jdew at vt.edu
Mon Sep 28 17:39:52 CEST 2009


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;


Any suggestions??? 
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