Re: [Matplotlib-users] matplotlib basemap streamlines plot

[Jody K. <jk...@uv...>]

Hi,

If your flow is actually non-divergent, so that continuous streamlines make sense, you could contour the streamfunction: a decent approximation should be
psi = 0.5*( cumsum(u*dy[:,newaxis],axis=1)-cumsum(v*dx[newaxis,:],axis=0))

Of course this won’t work so well if u and v are coarsely spaced or divergent...

Cheers,   Jody

> On Mar 30, 2015, at  20:26 PM, Tony Yu <ts...@gm...> wrote:
> 
> On Mon, Mar 30, 2015 at 2:15 PM, Foehn <fo...@po... <mailto:fo...@po...>> wrote:
> Am 2015-03-27 um 15:01 schrieb Sappy85:
> > Hi all,
> >
> > tried to plot a streamline with matplotlib. So far it work's.
> > But my question: Is there a possibility to avoid the gaps in the streamlines
> > (see my picture)?
> 
> I think the problem is that the streamline algorithm doesn't make any attempt to optimize for longer streamlines. It's been a long time since I've looked at the code, but roughly speaking, the algorithm optimizes for spacing between streamlines. Reducing the `minlength` input *should* slightly prefer longer streamlines, but you'll see side-effects with lines near borders and diverging flows.
> 
> If changing the `streamplot` implementation is an option, one of the simpler ways to achieve streamlines with fewer gaps would be allow the grid of starting points to vary independently from the grid that determines that streamlines are "too close". There are also "smarter" ways of seeding the streamlines, but that would be a bit more work, I believe.
> 
> -Tony
>  
> >
> > <http://matplotlib.1069221.n5.nabble.com/file/n45276/ff850_0.png <http://matplotlib.1069221.n5.nabble.com/file/n45276/ff850_0.png>>
> 
> Are you sure your flow is non divergent? Otherwise sinks and sources of
> streamlines are quite natural. If your flow is divergence free I I
> frankly admit that I have no idea how to solve the problem with the
> (then) spurious gaps.
> 
> Regards, Foehn
> 
> 
> >
> > Regards
> > Sappy85
> >
> > --
> > View this message in context: http://matplotlib.1069221.n5.nabble.com/matplotlib-basemap-streamlines-plot-tp45276.html <http://matplotlib.1069221.n5.nabble.com/matplotlib-basemap-streamlines-plot-tp45276.html>
> 
> 
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