R help - Apr 2013 - extract function extracting only NA values

Hello,

I have five raster files in ASCII format. With four of them I have no 
problem extracting values based on a set of X and Y coordinates. 
Unfortunately with one of the files all I managed to extract is NA 
values. To verify the problem I have opened the raster with ArcMap and 
there are no NA values where I am extracting. I have also plotted the 
spatial point class on top of the raster in R and it does correspond to 
the correct locations.

These are some of the commands I am using, and as I already pointed out 
that works perfectly with other raster files.

sp<-SpatialPoints(xysp)
xy$rasterimg<-extract(rasterimg,sp)

Can anyone help? At this point I am rather clueless about this.

Thanks

So I think I might have found what is causing this problem. The values I 
have in this raster

 > summary(ps0011yme)
                 layer
Min.        -9458.911
1st Qu.   1955256.000
Median   10618870.000
3rd Qu.  79577730.000
Max.    167780500.000
NA's            0.000

 From ArcMap though I get different values
min -69826224 and max 167780496

So maybe when I am importing the rest are in R something goes wrong and 
all the values below a certain threshold are considered NA. Is this a 
bug or do I get to use a specific parameter for the raster function?


On 4/24/2013 13:10, Fabio Berzaghi wrote:
> Hello,
>
> I have five raster files in ASCII format. With four of them I have no 
> problem extracting values based on a set of X and Y coordinates. 
> Unfortunately with one of the files all I managed to extract is NA 
> values. To verify the problem I have opened the raster with ArcMap and 
> there are no NA values where I am extracting. I have also plotted the 
> spatial point class on top of the raster in R and it does correspond 
> to the correct locations.
>
> These are some of the commands I am using, and as I already pointed 
> out that works perfectly with other raster files.
>
> sp<-SpatialPoints(xysp)
> xy$rasterimg<-extract(rasterimg,sp)
>
> Can anyone help? At this point I am rather clueless about this.
>
> Thanks
>
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