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

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

Dear John,

I see your points. However, after I changed to using add_artist. This is 
still nothing on the canvas. I think that there is some problem with the 
draw function of my arrow class. I have no idea what else should be 
there. At the moment, only one call in my case as below.

	def draw(self, renderer):
		self._stem.draw(renderer)

Could u tell what else should be called?

Best regards,
Chris

John Hunter wrote:
>>>>>>"Chris" == Chris  <bi...@Fu...> writes:
> 
> 
>     Chris> I tried with what you suggested to make an Arrow class. To
>     Chris> begin with, I only put an Line2D instance. I searched for
>     Chris> table stuff in axes.py, matlab.py to make the arrow
>     Chris> importable from matplotlib.matlab. Then I also try a very
>     Chris> very simple demo and I expect to see a simple
>     Chris> line. However, I can not see it. Could someone tell me what
>     Chris> is the problem. Here is my very very rudimental codes.
> 
> Nowhere in your code do you actually draw the arrows in self.arrows.
> In Axes.draw you would need to do
> 
>     for arrow in self.arrows: 
>         arrow.draw(renderer)
> 
> And this should work.
> 
> However, you can avoid all the overhead of add_arrow, and keeping a
> list of arrows in self.arrows simply by doing
> 
> 
>      def arrow(self, x, y, *args, **kwargs):
>          a = Arrow(x,y, *args, **kwargs)
>          self.add_artist(a)
>                  ^^^
>          return a
> 
> Ie, call add_artist which is a generic method for adding artists to
> the axes.
> 
> Hope this helps,
> JDH
> 
> 
> 
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