[R] estimate variance

[Francisco J. Zagmutt]

assuming your data is called dat, you can use:

tapply(dat$sc, INDEX=list(p=dat$p, aa=dat$aa), var)

see ?tapply and ?var

I hope this helps

Francisco



Aimin Yan wrote:
> I have data like this
> 
> aa    p   sc
> met  p1  34
> met  p1  56
> met  p2  45
> met  p2  33
> ser  p1  34
> ser  p1  56
> ser  p2  45
> ser  p2  33
> ....
> 
> I want to estimate the following variances for:
> sc in p1 for met
> sc in p2 for met
> sc between p1 and p2 for met
> sc for met
> 
> sc in p1 for ser
> sc in p2 for ser
> sc between p1 and p2 for ser
> sc for ser
> 
> 
> Does anybody how to write code for this?
> 
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