[R-sig-Geo] Converting Grid to factor list

[Ronnie Babigumira]

Edzer, Many thanks for this "aha...I see" moment. Most illuminating

Ronnie

Edzer J. Pebesma wrote:
> Ronnie Babigumira wrote:
> 
>> Edzer
>> Many thanks. The grid was created in ArcView and exported as an ascii 
>> file. I then read it in R using the read.asciigrid function in map tools
>>
>> Any ideas?
>>  
>>
> Yes; the function returns an object of class SpatialGridDataFrame:
> 
>  > example(read.asciigrid)
> 
> rd.scg> x <- read.asciigrid(system.file("external/test.ag",
>    package = "sp")[1])
> 
> rd.scg> class(x)
> [1] "SpatialGridDataFrame"
> attr(,"package")
> [1] "sp"
> 
> rd.scg> image(x)
>  > names(x)
> [1] "/home/edzer/S/library/sp/external/test.ag"
>  > names(x) = "foo"
>  > f = factor(round(x$foo))
>  > summary(f)
>    357     394     270     310     398     294     295     303     
> 307     391
>     18      18      17      17      17      16      16      16      
> 16      16
> [etc., etc.,...]
>    250     256     265     274     290     291     297     299 
> (Other)    NA's
>      9       9       9       9       9       9       9       9    
> 1938    6097
>  >
> 
> The renaming to foo was not necessary, but quotes would have
> been necessary around the name as it contained slashes. I rounded
> the values because they were numeric.
> -- 
> Edzer
> 
>> Ronnie
>>
>> Edzer J. Pebesma wrote:
>>  
>>
>>> Ronnie, you didn't tell us how you created the grid. Is it on of the
>>> grid classes in package sp? In that case you can address the
>>> variable in it by it's name, say foo:
>>>
>>> mygrid.f <- factor(mygrid$foo)
>>>
>>> hth,
>>> -- 
>>> Edzer
>>>
>>> Ronnie Babigumira wrote:
>>>
>>>   
>>>> Hi listers
>>>> I would like to change a grid to a factor list so as to apply Join 
>>>> Count statistics however when I use
>>>> mygrid.f <- factor(mygrid)
>>>>
>>>> I get an error message " 'x' must be atomic".
>>>>
>>>> Looking through the RHelp archives, I have chanced on emails with a 
>>>> similar problem but no direct answer to this. Is anyone farmiliar 
>>>> with this and how can I go about it
>>>>
>>>>
>>>> Many thanks
>>>>
>>>> Ronnie
>>>>
>>>> _______________________________________________
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>>>> R-sig-Geo at stat.math.ethz.ch
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>>>>
>>>>
>>>>     
>>>   
>>
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>>  
>>
> 
>