R help - Mar 2013 - vector field from a 3D scalar field

I have a 3D field of a scalar variable (x, y, z, value).  Is there a way to
generate a vector field from this data--gradient at defined points?  I found the
rasterVis package for 2D data, but as yet nothing for 3D data.

Thanks,
Scott Waichler
Pacific Northwest National Laboratory
Richland, WA
scott.waichler at pnnl.gov

On Mar 21, 2013, at 4:40 PM, Waichler, Scott R wrote:
> I have a 3D field of a scalar variable (x, y, z, value).  Is there a way to
generate a vector field from this data--gradient at defined points?  I found the
rasterVis package for 2D data, but as yet nothing for 3D data.
Can't you just think of 'value' as a "potential" and then
differentiate (using sweep?) along the three principal axes to construct the
partial derivatives (eg. diff(value)/diff(x) at constant y and z)  which would
then form the components of the vector field? That's how one goes from
gravitational or electrical potential to the corresponding vector fields. E
<- grad(V),

As always: Data would help clarify.

-- 
David Winsemius
Alameda, CA, USA