Streamslice in polar coordinates problem

Hey,

I'm struggling with my code, which should create streamlines of vector field in polar coordinates. I have converted (r, phi) components to normal cartesian coordinates (x,y). Components in terms of (r, phi) were distributed uniformly, it means for r = 0:const:10, phi = 0:const:2*pi. Now I'm trying to compute the streamlines of this vector field using streamslice(x,y,wx,wy), but I get an error:

streamslice(x,y,Gradx,Grady)
Error using griddedInterpolant
Interpolation requires at least two sample points in each
dimension.

Error in interp1 (line 151)
        F = griddedInterpolant(X,V,method);

Error in stream2 (line 62)
    sxi=interp1(xx(:),1:szu(2),sx(k));

Error in streamslice>nicestreams (line 313)
            vertsf = stream2(x,y, u,
            v,xstart,ystart,streamoptions);

Error in streamslice (line 138)
        [vertsout, avertsout] =
        nicestreams(x,y,u,v,density,arrows);

To be detailed, each matrix inside the streamline funtion has dimensions of 201x73.

I also tried to compute a little bit different streamslice:

streamslice(x',y',Gradx',Grady')

which sometimes worked for other people (yes, I've done my "research")... but it gives the same error message.

I also enclose quiver plot of this vector field if it could help someone. If someone helped mi with this problem I would be really grateful. Really, I don't have any idea.