plot vector in polar coordinates

["Vincent Echevin (LODYC)" <Vincent.Echevin@xxxxxxxxxxxxxxx>]

Dear Ferret-users,

We are trying to perform a vector plot
on a polar grid, that is:

we have a field u,v, on a grid 
theta=0:2.pi, r=0:1.

we transform these coordinates into cartesian coordinates,
x= r. cos(theta), y=r.sin(theta).

To visualize u (for example) on the cartesian grid, the command
"shade/l=1 u,x,y" works fine.

however how can we plot vectors on this grid?
"vector/l=1 u,v" plots the vector field on the initial grid.
is there a command like "vector u,x,y;v,x,y" ?

We would much appreciate any help!

Vincent Echevin & Pascale Bouruet-Aubertot