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.
Variance of a single number
3 messages · Adaikalavan Ramasamy, PIKAL Petr, Brian Ripley
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
On 10 Dec 2002 at 15:50, Adaikalavan Ramasamy wrote:
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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On Tue, 10 Dec 2002, Adaikalavan Ramasamy wrote:
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.
You are. It's an estimate of the population variance, about which there is no information at all in one number. Or just look at the formula, which gives 0/0.