[R] SAS-like method of recoding variables?

[David Freedman]

Frank, would you feel comfortable giving us the reference to the NEJM article
with the 'missing vs <' error ?  I'm sure that things like this happen
fairly often, and I'd like to use this example in teaching

thanks, david freedman


Frank E Harrell Jr wrote:
> 
> Dieter Menne wrote:
>> 
>> 
>> P.Dalgaard wrote:
>>>
>>>> IF TYPE='TRUCK' and count=12 THEN VEHICLES=TRUCK+((CAR+BIKE)/2.2);
>>> vehicles <- ifelse(TYPE=='TRUCK' & count=12, TRUCK+((CAR+BIKE)/2.2), NA)
>>>
>>>
>> 
>> Read both versions to an audience, and you will have to admit that this
>> is
>> one of the cases where SAS is superior.
> 
> Here's a case where SAS is clearly not superior:
> 
> IF type='TRUCK' AND count<12 THEN vehicles=truck+(car+bike)/2.2;
> 
> If count is missing, the statement is considered TRUE and the THEN is 
> executed.  This is because SAS considers a missing as less than any 
> number.  This resulted in a significant error, never corrected, in a 
> widely cited New England Journal of Medicine paper.
> 
> Frank
> 
>> 
>> Dieter
>> 
>> 
> 
> 
> -- 
> Frank E Harrell Jr   Professor and Chair           School of Medicine
>                       Department of Biostatistics   Vanderbilt University
> 
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> 

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