[R-sig-Geo] Help with conversion from NetCDF to ASCII

[Robert J. Hijmans]

If you really require square cells, then the resample function in
'raster' might be useful:

library(raster)
r = raster('ncdffile')
# or r=raster(matrix); extent(r) = c( , , , )
s = raster(r)
res(s) = min(res(s))
s = resample(r, s,  method='bilinear')
s = writeRaster(s, filename='abc.asc', format='ascii')

Or first do an interpolation first. Many options for that. E.g. see
?raster::interpolate

Robert

On Mon, Feb 1, 2010 at 2:49 PM, Michael Sumner <mdsumner at gmail.com> wrote:
> Does it have to be that ascii format? There are much better options
> for regular grids, such as GeoTIFF - but it depends on your target of
> course. Note that some software supports different dx/dy sizes, namely
> GDAL and Golden Surfer for this format:
>
> http://www.gdal.org/frmt_various.html#AAIGrid
>
> If it does need to be ESRI ASCII, you could write it out with square
> cells and then reset the cell sizes in the target (if possible).
>
> Is the requirement for square cells with the ESRI version of this
> format, or with the software you want to use next?
>
> As a last resort you could resample the grid using R's indexing/seq
> functions, or with spsample in package sp, or warp it with an external
> tool like gdalwarp.
>
> Cheers, Mike.
>
> On Tue, Feb 2, 2010 at 9:32 AM, Narayani Barve <narayani.ku at gmail.com> wrote:
>> Hi All,
>>
>> I want to convert netCDF files to ESRI ASCII grid. I used the package ncdf
>> to read the file and get the required variable in the matrix format. Now I
>> want to write this matrix into ESRI ASCII grid. Looking at the extends of
>> the data, and the row and column dimensions, I know that the CELLSIZE is not
>> square.
>>
>> Is there any way, I can convert this data into square ASCII Grid (ESRI)
>> format.
>>
>> Thanks,
>> Narayani
>>
>>        [[alternative HTML version deleted]]
>>
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