R help - May 2013 - need means on all boxplots, but only half of them got that

I tried to draw a point on all boxplots for their means, I did:

boxplot( Daten$weight~interaction(Daten$Dosis,Daten$sex, drop=TRUE))
means<-tapply( Daten$weight, Daten$Dosis, mean)
points(means, pch=5, col="red", lwd=5)

but only the boxplots for male got that point on them, its really weird
because I don't think that I separated the sex in the codes above

	[[alternative HTML version deleted]]

Hi,
? If the means are based on the combination.
means<-tapply( Daten$weight, list(Daten$Dosis,Daten$sex), mean)
library(reshape2)

points(melt(means)$value,pch=5,col="red",lwd=5)
A.K.



----- Original Message -----
From: maggy yan <kiotoqq at gmail.com>
To: R-help at r-project.org
Cc: 
Sent: Saturday, May 11, 2013 8:57 PM
Subject: [R]  need means on all boxplots, but only half of them got that

I tried to draw a point on all boxplots for their means, I did:

boxplot( Daten$weight~interaction(Daten$Dosis,Daten$sex, drop=TRUE))
means<-tapply( Daten$weight, Daten$Dosis, mean)
points(means, pch=5, col="red", lwd=5)

but only the boxplots for male got that point on them, its really weird
because I don't think that I separated the sex in the codes above

??? [[alternative HTML version deleted]]

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>boxplot( Daten$weight~interaction(Daten$Dosis,Daten$sex, drop=TRUE))
>means<-tapply( Daten$weight, Daten$Dosis, mean)
>points(means, pch=5, col="red", lwd=5)
>
> ...only the boxplots for male got that point on them, 
> its really weird because I don't think that I separated the sex in the
codes above
Look again; the boxplot is clearly distinguished by sex.

Try 
means<-tapply( Daten$weight, interaction(Daten$Dosis,Daten$sex, drop=TRUE),
mean)

S Ellison

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