[R] Obtaining midpoints of class intervals produced by cut and table

Peter Dalgaard p.dalgaard at biostat.ku.dk
Sun Nov 8 22:31:56 CET 2009


jose romero wrote:
> Hello list:
> 
> I am using "cut" and "table" to obtain a frequency table from a
numeric sample vector. The idea is to calculate mean and standard
deviation on grouped data. However, I can't extract the midpoints of the
class intervals, which seem to be strings treated as factors. How do i
extract the midpoint?
> 

You might consider starting with hist() instead. Otherwise, how about

mid <- brk[-1] - diff(brk)/2

where brk is the breakpoints used in cut()

-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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