Re: [Matplotlib-users] basemap: how to plot "toothed" curves

[Benjamin R. <ben...@gm...>]

Looks like someone else figured out a creative solution using quiver:
http://stackoverflow.com/questions/19918502/sawtooth-line-style-in-matplotlib

Here it is (slightly cleaned up):

import matplotlib.pyplot as pltimport numpy as np

x = np.linspace(0, 2*np.pi, 100)
y = np.sin(x)

dx = np.diff(x)
dy = np.diff(y)

x2 = np.linspace(0, 2*np.pi, 10)
y2 = np.sin(x2)

dx = np.zeros_like(x2) + 1e-12
dy = np.sin(x2 + dx) - y2

length = np.hypot(dx, dy)
dx /= length
dy /= length

fig, ax = plt.subplots()
ax.set_aspect("equal")
ax.plot(x, y, lw=4)

size = 20
ax.quiver(x2, y2, -dy, dx, headaxislength=size, headlength=size,
headwidth=size, color="blue")
plt.margins(0.2)


I don't know yet how to get rounded heads, though. Now I am looking to see
how the text box styles of "sawtooth" and "roundtooth" are handled in the
code to see if that could be exploited, instead.

Cheers!
Ben Root



On Fri, Oct 16, 2015 at 10:24 AM, Benjamin Root <ben...@gm...>
wrote:

> Hmmm, this is actually an interesting problem. I am also a meteorologist,
> so this is interesting to me.
>
> I haven't figured it out yet, but here are my thoughts:
>
> 1) There are the "^" triangle markers as well as "2" tri_up markers:
> http://nbviewer.ipython.org/github/WeatherGod/AnatomyOfMatplotlib/blob/master/AnatomyOfMatplotlib-Part3-HowToSpeakMPL.ipynb#Markers
> 2) The markevery property should be set to a float value to have the
> markers spaced out evenly along the line regardless of aspect ratios and
> zooming (note, this assumes that the line is defined with many vertices to
> give a smooth appearance).
>
> Problem:
> Using markers and markevery in a Line2D object has an inherent limitation:
> all of the markers will be drawn in the same orientation. So, we can't
> orient the markers along the normal of the line.
> Also, there is no pre-defined marker for half-circles, so this approach
> wouldn't work well for warm-fronts/dry-lines/etc.
>
> I'll have to see if a PolygonCollection + Line2D might be the right
> approach here...
>
> Ben Root
>
>
>
>
> On Fri, Oct 16, 2015 at 7:22 AM, Phil Cummins <phi...@an...>
> wrote:
>
>> Hi,
>>
>> I would like to plot "toothed" curves using basemap. These are curves
>> with triangles on one side, that are used to plot pressure fronts in
>> meteorology or thrust faults in geology. You need to be able to say which
>> side of the curve the triangles should appear on. Does anyone know whether
>> such curves can be plotted using mtplotlib/basemap?
>>
>> Thanks,
>>
>> - Phil
>>
>> Australian National University
>>
>>
>>
>>
>> ------------------------------------------------------------------------------
>>
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>>
>