[R] possible bug in sd

[Liaw, Andy]

> From: Claudio Agostinelli [mailto:mail-list at linaria.dst.unive.it]
> 
> Dear All,
> I think there is a small bug in sd when the argument is a 
> dataframe and
> there are missing values:
> 
> > x <- data.frame(matrix(rnorm(12,0,1), nrow=4, ncol=3))
> > x[1,1] <- NA
> > sd(x)
> Error in var(x, na.rm = na.rm) : missing observations in cov/cor
> > sd(x, na.rm=TRUE)
> Error in var(x, na.rm = na.rm) : missing observations in cov/cor
> > sapply(x, sd, na.rm=TRUE)
>        X1        X2        X3
> 1.0308198 0.4817945 1.5692881

That's because sd looks like the following:

function (x, na.rm = FALSE) 
{
    if (is.matrix(x)) 
        apply(x, 2, sd)
    else if (is.vector(x)) 
        sqrt(var(x, na.rm = na.rm))
    else if (is.data.frame(x)) 
        sapply(x, sd)
    else sqrt(var(as.vector(x), na.rm = na.rm))
}

Notice how the na.rm argument never got passed in the apply() and sapply()
calls.  I'd call that a bug alright.

Cheers,
Andy

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