R help - Jun 2009 - function to determine to which class/category a value belongs to?

Hi all,

I''ve got a simple contingency table produced with table(), and the
upper and
lower quartiles (quantile25 and quantile75) for the same dataset.
Is there a function that tells me in which category does the value of the
quartile falls into?

for example:

tabsp <- table(fam$I[fam$I>0])

1 3 6
6 1 1

and for the cumulative frequency distribution

tabcum <- cumsum(tabsp)

1 3 6
6 7 8

so, If my lower quartile is "2", I can visually determine that it
falls into
class/category "1" with 6 observations.  Is there a function that
performs
this determination?

Thanks.

Germán Bonilla
I. Ecol. UNAM

	[[alternative HTML version deleted]]

You might want to experiment with:

  ql <- cut( fam$I[fam$I>0], breaks =  quantile( fam$I[fam$I>0],  
type=1) , right=FALSE)
  levels(ql) <-
c("1stQ","2ndQ","3rdQ","4thQ")
  ql


cut() returns a factor. If you accept the default for the right  
parameter in cut, you will be pulling your hair out when dealig with a  
discrete variable.

On Jun 17, 2009, at 6:24 PM, Germ?n Bonilla wrote:
> Hi all,
>
> I've got a simple contingency table produced with table(), and the  
> upper and
> lower quartiles (quantile25 and quantile75) for the same dataset.
> Is there a function that tells me in which category does the value  
> of the
> quartile falls into?
I cannot quite parse this sentence. See if the example gives a  
meaningful result with your data, and read the help pages for quantile.
>
> for example:
>
> tabsp <- table(fam$I[fam$I>0])
>
> 1 3 6
> 6 1 1
>
> and for the cumulative frequency distribution
>
> tabcum <- cumsum(tabsp)
>
> 1 3 6
> 6 7 8
>
> so, If my lower quartile is "2", I can visually determine that it
> falls into
> class/category "1" with 6 observations.  Is there a function that
> performs
> this determination?
>
> Thanks.
>
> Germ?n Bonilla
> I. Ecol. UNAM
>
> 	[[alternative HTML version deleted]]
>
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Heritage Laboratories
West Hartford, CT