Message-ID: <508BB75D.6030709@stats.ox.ac.uk>
Date: 2012-10-27T10:28:45Z
From: Brian Ripley
Subject: why sd() can be applied to character vector?
In-Reply-To: <508BA659.7050201@yeah.net>
On 27/10/2012 10:16, Jinsong Zhao wrote:
> Hi there,
>
> In the following example, sd() can be applied to a character vector.
> However, mean() can not be run in a similar way. Why?
>
> I have read sd() man page, however, I don't find information about that
> behavior.
Well, it is there:
x: a numeric vector or an R object which is coercible to one by
?as.vector?.
> as.vector(x, 'numeric')
[1] 1 2 3 4 5 6 7 8 9 10
And it is different from mean() because that is generic and allows many
other forms of input, whereas for sd() one knows what to coerce to.
>
> > x <- as.character(1:10)
> > sd(x)
> [1] 3.02765
> > mean(x)
> [1] NA
> Warning message:
> In mean.default(x) : argument is not numeric or logical: returning NA
>
> Regards,
> Jinsong
>
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--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
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