[Matplotlib-users] Re: How to draw an arrow using matplotlib

[Chris <bi...@Fu...>]

Thanks a lot for the very very detail reply. I can not find the time to 
do it by myself at the moment. I will come back to this issue again 
after 2 two weeks.

Best regards,
Chris

John Hunter wrote:
>>>>>>"Chris" == Chris  <Ch...@Fu...> writes:
> 
> 
>     Chris> Dear friends, I just start to use matplotlib, which looks
>     Chris> quite promising for me. I need to draw a couple of arrows
>     Chris> in my 2D plot. Is there a simple way to get it work?
> 
>     Chris> Any suggustions are welcome.
> 
> I recommend creating an arrow class, derived from matplotlib.artist.Artist, that
> contains a matplotlib.lines.Line2D for the arrow stem and a
> matplotlib.patches.RegularPolygon  with numVertices=3 for the arrow
> head.  You can control the rotation of the arrowhead with the
> orientation argument.  
> 
> Once you have this class so defined, you can add it instances of it to
> the axes with ax.add_artist(arrow).
> 
> I'll be happy to help out with a prototype if you have trouble.  Take
> a look at matplotlib.table.Cell, which John Gill wrote to support
> tables.  You can use this as a simple model for how to write new
> artists (things that draw into a figure) composed of other artists.
> 
> It would be nice to have a fancy arrow class, that supported text
> labeling, at the base, along the stem and at the arrowhead.  You could
> also consider a more sophisticated polygon other than a triangle for
> the arrowhead.
> 
> Finally, if you needed to draw *a lot of arrows*, order of a thousand
> or more (eg for direction fields), a
> matplotlib.collections.PolygonCollection would be the way to go for
> efficiency.
> 
> JDH
> 
> 
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