[STATSGRASS] R-GRASS scripting question

[Thomas Adams]

Roger & Edzer,

Thanks for your help! That did the trick.

Regards,
Tom

Roger Bivand wrote:

>On Fri, 23 Jan 2004, Edzer J. Pebesma wrote:
>
>  
>
>>Thomas Adams wrote:
>>
>>    
>>
>>>Roger (or anyone else),
>>>
>>>I am at an impasse attempting to write an R script to call from within 
>>>GRASS. Attached is a code fragment. Basically, I can not get beyond:
>>>
>>>summary(bias$mapname)
>>>      
>>>
>>You want the value of mapname to be evaluated: the content is not in
>>bias$mapname but bias$something, with something the value of the
>>variable mapname.
>>
>>Try:
>>
>>summary(bias[[eval(mapname)]]
>>    
>>
>
>Yes, this is right. There may be a short cut, if you know definitely for 
>example that there is just one raster in the bias list. Then you access it 
>by number, for example:
>
>summary(bias[[1]])
>
>The same would apply if there were more, but then it would be easier to 
>get mixed up.
>
>  
>
>>a <- list(a=NA, b=Inf)
>>a
>>    
>>
>$a
>[1] NA
>
>$b
>[1] Inf
>
>  
>
>>a$a
>>    
>>
>[1] NA
>  
>
>>a[[1]]
>>    
>>
>[1] NA
>  
>
>>a[["a"]]
>>    
>>
>[1] NA
>  
>
>>an <- "a"
>>a$an
>>    
>>
>NULL
>
>(no such element in list)
>
>  
>
>>a[[eval(an)]]
>>    
>>
>[1] NA
>
>Roger
>
>  
>
>>--
>>Edzer
>>
>>
>>    
>>
>
>  
>

-- 
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177

EMAIL:	thomas.adams at noaa.gov

VOICE:	937-383-0528
FAX:	937-383-0033

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