R devel - Oct 2007 - meaning of "trim" in mean()

(I see this in both R-patched r43124 and R-devel r43233.)
In the Argument section of ?mean:

trim     the fraction (0 to 0.5) of observations to be trimmed from each
end of x before the mean is computed. Values outside that range are
taken as the nearest endpoint.  

Then in the Value section:

If trim is non-zero, a symmetrically trimmed mean is computed with a
fraction of trim observations deleted from each end before the mean is
computed.

The description in "trim" to me sounds like Windsorizing, rather than
trimming.  Should that be edited?

Best,
Andy


Andy Liaw, PhD
Biometrics Research    PO Box 2000 RY33-300
Merck Research Labs        Rahway, NJ 07065
andy_liaw(a)merck.com          732-594-0820



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Liaw, Andy wrote:
> (I see this in both R-patched r43124 and R-devel r43233.)
> In the Argument section of ?mean:
>
> trim     the fraction (0 to 0.5) of observations to be trimmed from each
> end of x before the mean is computed. Values outside that range are
> taken as the nearest endpoint.  
>
> Then in the Value section:
>
> If trim is non-zero, a symmetrically trimmed mean is computed with a
> fraction of trim observations deleted from each end before the mean is
> computed.
>
> The description in "trim" to me sounds like Windsorizing, rather
than
> trimming.  Should that be edited?
>
>   
I think so:
> x <- sort(rnorm(10))
> mean(x,trim=.1)
[1] -0.6387413
> mean(x[2:9])
[1] -0.6387413
> mean(x[c(2,2:9,9)]) # Winsorizing
[1] -0.6204222

So yes, it is trimming, not Winsorizing, and the last sentence in the
description of "trim" is misleading and should be, well..., trimmed.

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