[R] Classifying values by interval

[Ted Harding]

Thanks, Dimitris. That looks hopeful!
Ted.

On 31-Aug-11 08:06:23, Dimitris Rizopoulos wrote:
> Probably you're looking for function findInterval().
> 
> I hope it helps.
> 
> Best,
> Dimitris
> 
> On 8/31/2011 10:00 AM, Ted Harding wrote:
>> Greetings All!
>> As is often the case on this list, the answer may well
>> be under my nose but I can't see it!
>>
>> I am looking for a "smart" way to do the following.
>>
>> Say I have a vector of values, X. I set up bins" for X,
>> say with breaks at B = c(b1,b2,...,b11) covering the
>> range of X, i.e. bins numbered 1:10. The value x is in
>> bin i if B[i]<  x<= B[i+1]
>>
>> What I seek is a vector, of the same length as X, which
>> for each x in X gives the number of the bin that x is in.
>>
>> Clearly this can be done in an "unsmart" way by looping
>> through all of X along with something like
>>
>>    which( (B[1:10]<  X[j])&  (X[j]<= B[2:11]) )
>>
>> However, I feel that this naturally occurring task must
>> have received a smarter solution! The hist() function
>> already does this implicitly, since it has to decide
>> which bin a value in X should be counted in. But it
>> apparently then discards this information, since there
>> is nothing relevant in the return values from hist().
>>
>> So is there a "smart" function somewhere for this?
>>
>> The motivation here is that I have multivariate data,
>> (X,Y,Z,...) and I wish to study how it behaves in each
>> different bin for X. So the "bin index", ixB aY, derived
>> for X can be applied to select corresponding subsets of
>> the other variables. Rather than doing it the clumsy
>> way each time, e.g. according to
>>
>>    Y[(B[i]<  X)&  (X<= B[j+1])]
>>
>> I would like to have the bin index permanently available
>> -- for example it allows easy logical combinations of
>> bins, such as Y[(ixB==j1) | (ixB==j2)], or Y[(ixB %in% ixB0)].
>>
>> With thanks,
>> Ted.
>>
>> --------------------------------------------------------------------
>> E-Mail: (Ted Harding)<ted.harding at wlandres.net>
>> Fax-to-email: +44 (0)870 094 0861
>> Date: 31-Aug-11                                       Time: 09:00:27
>> ------------------------------ XFMail ------------------------------
>>
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> 
> -- 
> Dimitris Rizopoulos
> Assistant Professor
> Department of Biostatistics
> Erasmus University Medical Center
> 
> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
> Tel: +31/(0)10/7043478
> Fax: +31/(0)10/7043014
> Web: http://www.erasmusmc.nl/biostatistiek/

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E-Mail: (Ted Harding) <ted.harding at wlandres.net>
Fax-to-email: +44 (0)870 094 0861
Date: 31-Aug-11                                       Time: 09:14:19
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