[STATSGRASS] NULL values and readRAST6

[Markus Neteler]

Roger Bivand wrote:
> 
> On Tue, 9 Oct 2007, Roger Bivand wrote:
>> On Tue, 9 Oct 2007, Carlos "Guâno" Grohmann wrote:
>>
>>>  Hi,
>>>  Can readRAST6 handle NULL values? How?
>>>
>>>  I tried NODATA=NULL but it needs a numeric value..
>>
>> This is passed to r.out.bin, which says:
>>
>> null=integer
>>     Value to write out for null
>>     Default: 0
>>
>> so in fact it has to be an integer - I'll fix the documentation and
>> function 
>> (which didn't check what value was assigned to NODATA).
> 
> To make this a bit clearer - the raster layer in GRASS has missing values 
> set to NULL, but NULL cannot be exported by r.out.bin. So r.out.bin is 
> given a NODATA value to assign to NULL cells, which are then read into R, 
> and the NODATA valued cells are set to NA. The only need for the value is 
> to keep r.out.bin (and r.in.bin) happy, because they do not encode NULL 
> directly.
> 
> Roger
> 

Could this be automated by using 
r.info -r map
to get the range and then auto-use a value outside
of this range as NULL encoder and something in R with
min()/max() to do the same in the other direction?

But maybe I misunderstand the problem.

Markus
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