[R] SAS-like method of recoding variables?

[Peter Dalgaard]

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.
> 
> Dieter
> 
> 

That's not entirely clear. For instance, SAS is not being clear about 
what happens when the condition is FALSE.

SAS is also not distinguishing comparison and assignment, but then again 
you don't accidentally do count=12 when you mean count==12....

As a generic matter, SAS (the DATA step) is generally good at things 
that are done by sequential sweeps through a data file. The shortcomings 
come in when you do things that can't be done sequentially, or require 
substantial rearranging of data first. x - ave(x,g,median) is an example 
which IIRC requires

proc sort
proc means by group (saving medians to data set)
data step (merge and subtract)

On the third (!) hand, some other things require rethinking in R that 
are easily expressed in a sequential setting. "Last observation carried 
forward" comes to mind (notwithstanding theoretical issues of that 
procedure).


-- 
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