[R] vector density plot

[Jinsong Zhao]

Hi there,

Is there a function in R that can draw vector density plot? The vector 
density plot example can be found here:
http://reference.wolfram.com/mathematica/ref/VectorDensityPlot.html

As for the vector field plot, I found a function that has been posted in 
this mailing list:
https://stat.ethz.ch/pipermail/r-help/2007-November/147005.html

I also referred to rasterVis package for the vectorplot function. 
However, I don't figure out how to plot for field (-y, x) or something 
like that.

Any help will be really appreciated.

Best,
Jinsong