Variance of a single number

Most probably:


     The denominator n - 1 is used which gives an unbiased 
estimator of
     the (co)variance for i.i.d. observations. These functions return
     `NA' when there is only one observation (whereas S-plus has 
been
     returning `NaN'), and from R 1.2.3 fail if `x' has length zero.

from help page for var

try
?var

Just out of curiosity, can some please explain the following return
NA.

x <- 6
var(x)

y <- c( NA, NA, 10000 )
var(y, na.rm=T)


Unless I am seriously misguided, I believe that the variance of a
single number (i.e. a constant) should be zero. Thanks.

Regards, Adai.

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Petr Pikal
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p.pik at volny.cz