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

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

Hello again,
We had one more thought, which is just another way of doing what I
described yesterday. The polymark.jnl script takes pre-defined polygon
shapes and overlays them on a plot using the polygon command. It has a
scale parameter that would let you change the size of the polygons.
polymark.jnl calls a second script called polyshape.jnl. You could
modify this script, adding the definition of your curved arrow shape.
You could also modify polymark.jnl to add a new argument which would be
an angle of rotation for the arrow shape.

To locate these scripts, use the Unix command Fgo,

> Fgo polymark
> Fgo polyshape

If you come up with a solution you like, we encourage you to submit it
back to the Users Group as a contributed script.

Ansley

Ansley Manke wrote:

>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
>>
>>    
>>