R help - Jan 2012 - Quantiles in boxplot‏

Hi,

I have a simple question about quartiles in R, especially how they are
calculated using the boxplot.
Quartiles
 (.25 and .75) in boxplot are different from the summary function and 
also don't match with the 9 types in the quantile function.
See attachment for details.
Can you give me the details on how the boxplot function does calculate these
values?

Cheers,
Rene Brinkhuis (Netherlands) 		 	   		  
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The explanation is in ?boxplot.stats (as the help for boxplot states).

Details:

     The two ?hinges? are versions of the first and third quartile,
     i.e., close to ?quantile(x, c(1,3)/4)?.  The hinges equal the
     quartiles for odd n (where ?n <- length(x)?) and differ for even
     n.  Whereas the quartiles only equal observations for ?n %% 4 =     1? (n =
1 mod 4), the hinges do so _additionally_ for ?n %% 4 =     2? (n = 2 mod 4),
and are in the middle of two observations
     otherwise.

And so on, with references.

Sarah

2012/1/13 Ren? Brinkhuis <rene.brinkhuis at
live.nl>:
>
> Hi,
>
> I have a simple question about quartiles in R, especially how they are
calculated using the boxplot.
> Quartiles
> ?(.25 and .75) in boxplot are different from the summary function and
> also don't match with the 9 types in the quantile function.
> See attachment for details.
> Can you give me the details on how the boxplot function does calculate
these values?
>
> Cheers,
> Rene Brinkhuis (Netherlands)



-- 
Sarah Goslee
http://www.functionaldiversity.org