Re: [ferret_users] How to draw a curved arrow?

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Xia,
There is not a direct way to do this in Ferret. You would need to define
the outlines of the arrows you want and draw them as filled polygons.
The idea is like the one used in this example which defines a triangular
polygon and then places it in several locations on the plot where the
locations are set by XPTS and YPTS

*yes? LET xtriangle = YSEQUENCE({-1,0,1})
yes? LET ytriangle = YSEQUENCE({-1,1,-1})
yes? LET xpts = {152,188,142}
yes? LET ypts = {33,37,22}
yes? GO basemap x=100:200 y=0:50 20
yes? POLYGON/OVER xtriangle+xpts, ytriangle+ypts
*

Defining the curved arrows that you wish to use would be tedious but
once you have the shape you want you can reuse it. You can specify a
color palette on the POLYGON command to choose the color or colors you
want. The variables xtriangle and ytriangle (or your variables defining
the polygon shape) could be multiplied by a scale factor, or separate
scale factors for X and Y, to make the polygons the desired size. For
example, compare this polygon command:
*
yes? POLYGON/OVER/PALETTE=red 3*xtriangle+xpts, 2*ytriangle+ypts*

Ansley

Xia Changshui wrote:

>Dear colleagues,
>  As a new hand using Ferret, I have a question. I want to draw a curved arrow over a current filed to indicate the circulation is clockwise or anti-clockwise. Just like the blue curved arrow in the figure in the attached pdf file. How to achieve this? Can a simple command work? 
>Thank you in advance.
>Xia Changshui
>2005-11-25
>