Re: plot vector in polar coordinates

[Jonathan Callahan <callahan@xxxxxxxxxxxxx>]

Vincent and Pascale,

Sorry for the long delay in answering.

The vector command you desire is available in Ferret v5.0 as

VECTOR U,V,X,Y

This will plot the vectors on your "curvilinear" grid.

This capability is only released as an "alpha" version, i.e.
it is not quite robust yet.  There are some problems with 
the lengths of vectors and with drawing vectors across the
region boundaries.  It does give a qualitative sense of the
data but it is not yet quantitative in the manner that vectors
in Ferret normally are.

Try it out and we'll work at this end to make it more robust 
for the next release of Ferret.


-- Jonathan Callahan


> 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