This is more complicated than it looks because your raster encompasses 
more than 110 degrees of latitude! With such a large area  you cannot 
ignore the curvature of the surface of Earth.  If you do a regular grid 
in degrees as you want, the area of each cell will vary with latitude.  
So you either have a regular grid in degrees, but with varying cell 
area, or you will have to transform your data and define your raster in 
an adequate projection (e.g. an equal area projection).

Julian

-- 
Julian Mariano Burgos, PhD
Hafrannsóknastofnunin/Marine Research Institute
Skúlagata 4, 121 Reykjavík, Iceland
Sími/Telephone : +354-5752037
Bréfsími/Telefax:  +354-5752001
Netfang/Email: julian@hafro.is



On 02/20/2013 01:48 PM, Josep M Serra diaz wrote:
> Check function
>
> aggregate () in raster package
>
>
>
> 2013/2/20 Ross Ahmed <rossahmed@googlemail.com>
>
>> I have the following raster:
>>
>> myRaster <- c(-176.5813, 174.1103, -31.16667, 83.1)
>> myRasterExtent <- extent(matrix(myRaster, ncol=2, nrow=2, byrow=T))
>> myRasterExtent <-  raster(myRasterExtent, crs="+proj=longlat +ellps=WGS84
>> +datum=WGS84²)
>>
>> How can I change resolution to 100km^2 and 1000km^2
>>
>> many thanks
>> Ross
>>
>>
>>
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