Function builtin_var 

fn builtin_var(
    args: &[RValue],
    named: &[(String, RValue)],
) -> Result<RValue, RError>

Sample variance (Bessel-corrected, divides by n-1).

@param x numeric vector @param na.rm logical; if TRUE, remove NAs before computing @return scalar double (NA if input contains NAs and na.rm is FALSE)