Re: tapply()

[Terry Therneau <therneau@mayo.edu>]

Winnie Lambert asks how to get tapply to report numbers for a fixed set
of levels, i.e.,
        temp <- tapply(x, hours, mean)
        
where "hours" has numbers from 1 to 24, but in certain data sets not all of
the hours of the day have a representative.

 To get all of the hours, use
        temp <- tapply(x, factor(hours, levels=1:24), mean)
                
This will result in a solution vector of length 24, containing NA for levels
that did not occur.
        
        
                Terry Therneau