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

[Phil Cummins]

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

[Benjamin Root]

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 
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
> Matplotlib-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>
>
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Re: [Matplotlib-users] basemap: how to plot "toothed" curves

[Benjamin Root]

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 
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 
> 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
>> Matplotlib-users@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>
>>
>
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Re: [Matplotlib-users] basemap: how to plot "toothed" curves

[Phil Cummins]

Wow, that's fantastic Ben. Thanks so much for finding that, it's just 
what I need!

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 > 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
> 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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