# Plotting a vector field with polar coordinates on a ring

Assuming I have a vector components: A_r(r,theta) and A_t(r,theta) so A=(A_r,A_t)
I would like to show the Vector A on a ring. for some reason when I’m using VectorPlot it has to be in cartesian coordinates. So I have define A_x and A_y from A(r,t) and tried to use VectorPlot yet it shows nothing.
the line:

``````VectorPlot({ar(r, t), at(r, t)}, {r, R1, R2}, {t, 0, 2pi})
``````

shows a vector field, yet it is not on a ring.
when I’m trying to use the cartesian coordinates:

``````VectorPlot({FullSimplify(ax(x, y)), FullSimplify(ay(x, y))}, {x, -R2, R2}, {y, -R2, R2}, RegionFunction -> Function({x, y}, R1^2 < x^2 + y^2 < R2^2))
``````

It shows nothing.
I have made the transformation by

``````A_x=A_r(sqrt(x^2+y^2),Arctan(x,y))*(x/sqrt(x^2+y^2))-A_t(sqrt(x^2+y^2),Arctan(x,y))*(y/sqrt(x^2+y^2))

A_y=A_r(sqrt(x^2+y^2),Arctan(x,y))*(y/sqrt(x^2+y^2))+A_t(sqrt(x^2+y^2),Arctan(x,y))*(x/sqrt(x^2+y^2))
``````

For some reasons it does not work,
Any help?