Agus,

I am guessing that you are using a very small extent (probably derived from
the occurrence points) and that this extent covers far less than 500 raster
cells, and that it is therefore impossible to sample that many points (grid
cells; without replacement) from that area. If I am right, either use a
larger area, or fewer points.

Robert


On Thu, Dec 8, 2011 at 3:43 PM, agus <agus.camacho@gmail.com> wrote:

> Dear all,
>
> I am trying to use the function "randomPoints" for modelling distribution
> from a very low number of occorrences:
>
>    Longitude  Latitude
> 161  144.6333 -18.11667
> 163  144.0000 -18.03333
> 164  144.5500 -18.21667
> 165  144.6167 -18.1166
>
> I am using parameters as explained in the SDM in R pdf:
>
> However, despite this workedd well for species with a greater number of
> occurrences, this time it showed me the following error message:
>
> "Error en randomPoints(AU.environment, n = 500, ext = ext, tryf = 100,  :
>  generated random points = 0.06 times requested number; Use a higher value
> for tryf"
>
> I tried values of tryf about100, but still got the same result. Anyone
> might
> throw some light on this?
>
> Thanks a lot!
> Agus Camacho
>
> --
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>
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