Re: [R] Continous variables with implausible transformation?

From: zhu yao <mailzhuyao_at_gmail.com>
Date: Fri, 04 Jun 2010 08:38:03 +0800

THX Yao Zhu
Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China

2010/6/4 Frank E Harrell Jr <f.harrell_at_vanderbilt.edu>

> On 06/03/2010 11:32 AM, Joris Meys wrote:
>
>> You're right, it is the same. using I() won't work for the same reason
>> sqrt
>> don't, so :
>>
>> x2<- x^2
>>> lrm(y~x+x2)
>>>
>>
>> Thx for the correction.
>> Cheers
>> Joris
>>
>> On Thu, Jun 3, 2010 at 6:14 PM, Bert Gunter<gunter.berton_at_gene.com>
>> wrote:
>>
>> Below. -- Bert
>>>
>>> Bert Gunter
>>> Genentech Nonclinical Biostatistics
>>> --------------------------------------
>>> But you wrote linear+ square. Don't you mean:
>>> lrm(Y~x+x^2)
>>>
>>> --- I believe this is the same as lrm(Y ~ x).
>>> You must protect the x^2 via
>>>
>>> lrm(Y ~ x + I(x^2))
>>>
>>
> But don't use that construct. Use lrm(Y ~ pol(x, 2))
>
> Frank
>
>
>>> ------------------------------------------
>>>
>>> --
>>>
>> Joris Meys
>> Statistical Consultant
>>
>> Ghent University
>> Faculty of Bioscience Engineering
>> Department of Applied mathematics, biometrics and process control
>>
>> Coupure Links 653
>> B-9000 Gent
>>
>
>
> --
> Frank E Harrell Jr Professor and Chairman School of Medicine
> Department of Biostatistics Vanderbilt University
>
> ______________________________________________
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