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

Regards,

- Phil

Benjamin Root wrote:

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.pyplotas  plt
import  numpyas  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.v.r...@gmail.com <mailto:ben.v.r...@gmail.com>> 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
    <phil.cumm...@anu.edu.au <mailto:phil.cumm...@anu.edu.au>> 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



        
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--

Phil Cummins
Prof. Natural Hazards
Research School of Earth Sciences
Australian National University

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