[R] Multiple missing values

[Frank E Harrell Jr]

Patrick Burns wrote:
> I can think of a few solutions, none perfect.
> 
> * You could have a master dataset that has the
> missing value codes you want, and a dataset that
> you use which is a copy of it with real NA's in it.
> 
> * You could add an attribute that gives the types
> of missing values in the various positions.  The
> downside is that attributes tend to disappear with
> subsetting.

The sas.get function in the Hmisc exemplifies that approach, and it has 
a subsetting method that preserves the special.miss attribute.

Frank

> 
> * If you only have two types, you might be able to
> get away with using NaN as the second type of NA.
> 
> On 14/02/2010 14:33, John wrote:
>> Does anyone know, or know documentation that describes, how to declare
>> multiple values in R as missing that does not involve coding them as 
>> NA? I
>> wish to be able to treate values as missing, while still retaining codes
>> that describe the reason for the value being missing.
>>
>> Thanks
>>
>> John MAcInnes
>>
>>
>>
-- 
Frank E Harrell Jr   Professor and Chairman        School of Medicine
                      Department of Biostatistics   Vanderbilt University