Thread: [Matplotlib-users] How to plot straight lines on polar plots

Hi,

Im having some trouble with this "seemingly" simple task of plotting
straight lines/fitted curves on a polar plot.

I am trying to create a plot that resembles the layout of the chart seen
below:

http://www.nabble.com/file/p21721073/brisbane.png 



So far I have only been able to plot data like so:

http://www.nabble.com/file/p21721073/AzvAlt.png 


The blue line should be similar to the bottom line of the first example
plot. The line would ultimately be formed by fitting a straight line/curve
through the points, instead of the way matplotlib is plotting.

I am plotting tuples of values (az and alt), and plotting using:


ax.plot(az, alt, 'b')
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I don't see any elegant way to do that.

The easiest way I can think of is to use a derived line2d class.
Something like below will work. Others may have better ideas.


import matplotlib.lines

class Line2DNoInterpolation(matplotlib.lines.Line2D):

    def recache(self):
        matplotlib.lines.Line2D.recache(self)
        self._transformed_path.get_transformed_path_and_affine = \
               self._transformed_path.get_transformed_points_and_affine



ax = subplot(111, projection="polar")

r = np.arange(0, 1.0, 0.1)
theta = 2*np.pi*r

p2 = Line2DNoInterpolation(theta, r, color='r', lw=1)
ax.add_line(p2)


-JJ


On Thu, Jan 29, 2009 at 12:20 AM, jamesf0 <ja...@ut...> wrote:
>
> Hi,
>
> Im having some trouble with this "seemingly" simple task of plotting
> straight lines/fitted curves on a polar plot.
>
> I am trying to create a plot that resembles the layout of the chart seen
> below:
>
> http://www.nabble.com/file/p21721073/brisbane.png
>
>
>
> So far I have only been able to plot data like so:
>
> http://www.nabble.com/file/p21721073/AzvAlt.png
>
>
> The blue line should be similar to the bottom line of the first example
> plot. The line would ultimately be formed by fitting a straight line/curve
> through the points, instead of the way matplotlib is plotting.
>
> I am plotting tuples of values (az and alt), and plotting using:
>
>
> ax.plot(az, alt, 'b')
> --
> View this message in context: http://www.nabble.com/How-to-plot-straight-lines-on-polar-plots-tp21721073p21721073.html
> Sent from the matplotlib - users mailing list archive at Nabble.com.
>
>
> ------------------------------------------------------------------------------
> This SF.net email is sponsored by:
> SourcForge Community
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> Mat...@li...
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>

I'm embarrassed to see that I neglected to document this, but you can 
pass a "resolution" keyword argument to add_axes which sets the number 
of points of interpolation between each pair of data points.  Set this 
to 1 to disable interpolation.

This will be documented shortly.

Mike

jamesf0 wrote:
> Hi,
>
> Im having some trouble with this "seemingly" simple task of plotting
> straight lines/fitted curves on a polar plot.
>
> I am trying to create a plot that resembles the layout of the chart seen
> below:
>
> http://www.nabble.com/file/p21721073/brisbane.png 
>
>
>
> So far I have only been able to plot data like so:
>
> http://www.nabble.com/file/p21721073/AzvAlt.png 
>
>
> The blue line should be similar to the bottom line of the first example
> plot. The line would ultimately be formed by fitting a straight line/curve
> through the points, instead of the way matplotlib is plotting.
>
> I am plotting tuples of values (az and alt), and plotting using:
>
>
> ax.plot(az, alt, 'b')
>   

-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Thanks for the help, but I can't quite see where to add the add_axes code.
Here is the code I have been using to plot, the polar plot is a subplot.

fig=figure()
ax=fig.add_subplot(111, polar=True)
ax.set_xticklabels(["E",45,"N",315,"W",225,"S",135])
ax.set_yticklabels([80,70,60,50,40,30,20,10])

...

ax.plot(az, alt, 'b')
fig.savefig('AzvAlt.png')
show()




Michael Droettboom-3 wrote:
> 
> I'm embarrassed to see that I neglected to document this, but you can 
> pass a "resolution" keyword argument to add_axes which sets the number 
> of points of interpolation between each pair of data points.  Set this 
> to 1 to disable interpolation.
> 
> This will be documented shortly.
> 
> Mike
> 
> jamesf0 wrote:
>> Hi,
>>
>> Im having some trouble with this "seemingly" simple task of plotting
>> straight lines/fitted curves on a polar plot.
>>
>> I am trying to create a plot that resembles the layout of the chart seen
>> below:
>>
>> http://www.nabble.com/file/p21721073/brisbane.png 
>>
>>
>>
>> So far I have only been able to plot data like so:
>>
>> http://www.nabble.com/file/p21721073/AzvAlt.png 
>>
>>
>> The blue line should be similar to the bottom line of the first example
>> plot. The line would ultimately be formed by fitting a straight
>> line/curve
>> through the points, instead of the way matplotlib is plotting.
>>
>> I am plotting tuples of values (az and alt), and plotting using:
>>
>>
>> ax.plot(az, alt, 'b')
>>   
> 
> -- 
> Michael Droettboom
> Science Software Branch
> Operations and Engineering Division
> Space Telescope Science Institute
> Operated by AURA for NASA
> 
> 
> ------------------------------------------------------------------------------
> This SF.net email is sponsored by:
> SourcForge Community
> SourceForge wants to tell your story.
> http://p.sf.net/sfu/sf-spreadtheword
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> 
> 

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Hello,

>>> I am trying to create a plot that resembles the layout of the chart seen
>>> below:
>>>
>>> http://www.nabble.com/file/p21721073/brisbane.png 
are you actually trying to plot sun path digrams?

May you share a part of your code once it is completed?

I'd be very interested in seeing a working example.

Kind regards,
Timme

Yeah "trying" to plot sun paths.

I'll be more than happy to share once it's complete.

James.


Timmie wrote:
> 
> Hello,
> 
>>>> I am trying to create a plot that resembles the layout of the chart
>>>> seen
>>>> below:
>>>>
>>>> http://www.nabble.com/file/p21721073/brisbane.png 
> are you actually trying to plot sun path digrams?
> 
> May you share a part of your code once it is completed?
> 
> I'd be very interested in seeing a working example.
> 
> Kind regards,
> Timme
> 
> 
> ------------------------------------------------------------------------------
> This SF.net email is sponsored by:
> SourcForge Community
> SourceForge wants to tell your story.
> http://p.sf.net/sfu/sf-spreadtheword
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
> 
> 

-- 
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jamesf0 <ja...@ut...> writes:

> Thanks for the help, but I can't quite see where to add the add_axes code.
> Here is the code I have been using to plot, the polar plot is a subplot.

> ax=fig.add_subplot(111, polar=True)

Change this to

  ax=fig.add_subplot(111, polar=True, resolution=1)

and the resolution will get passed to the PolarAxes instance.

-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Sorry, I have done that change, and get these errors:


Traceback (most recent call last):
  File "test7.py", line 36, in <module>
    ax=fig.add_subplot(111, polar=True, resolution=1)
  File "/usr/lib/python2.5/site-packages/matplotlib/figure.py", line 676, in
add_subplot
    a = subplot_class_factory(projection_class)(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/matplotlib/axes.py", line 6823, in
__init__
    self._axes_class.__init__(self, fig, self.figbox, **kwargs)
  File "/usr/lib/python2.5/site-packages/matplotlib/projections/polar.py",
line 171, in __init__
    Axes.__init__(self, *args, **kwargs)
  File "/usr/lib/python2.5/site-packages/matplotlib/axes.py", line 537, in
__init__
    if len(kwargs): martist.setp(self, **kwargs)
  File "/usr/lib/python2.5/site-packages/matplotlib/artist.py", line 894, in
setp
    func = getattr(o,funcName)
AttributeError: 'PolarAxesSubplot' object has no attribute 'set_resolution'





Jouni K. Seppänen wrote:
> 
> Change this to
> 
>   ax=fig.add_subplot(111, polar=True, resolution=1)
> 
> and the resolution will get passed to the PolarAxes instance.
> 
> -- 
> Jouni K. Seppänen
> http://www.iki.fi/jks
> 

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On Fri, Jan 30, 2009 at 12:28 AM, jamesf0 <ja...@ut...> wrote:
>
> Sorry, I have done that change, and get these errors:
>
>
> Traceback (most recent call last):
>  File "test7.py", line 36, in <module>
>    ax=fig.add_subplot(111, polar=True, resolution=1)
>  File "/usr/lib/python2.5/site-packages/matplotlib/figure.py", line 676, in
> add_subplot
>    a = subplot_class_factory(projection_class)(self, *args, **kwargs)
>  File "/usr/lib/python2.5/site-packages/matplotlib/axes.py", line 6823, in
> __init__
>    self._axes_class.__init__(self, fig, self.figbox, **kwargs)
>  File "/usr/lib/python2.5/site-packages/matplotlib/projections/polar.py",
> line 171, in __init__
>    Axes.__init__(self, *args, **kwargs)
>  File "/usr/lib/python2.5/site-packages/matplotlib/axes.py", line 537, in
> __init__
>    if len(kwargs): martist.setp(self, **kwargs)
>  File "/usr/lib/python2.5/site-packages/matplotlib/artist.py", line 894, in
> setp
>    func = getattr(o,funcName)
> AttributeError: 'PolarAxesSubplot' object has no attribute 'set_resolution'

What version of mpl are you using?  This should be fixed for releases >= 0.98.4

JDH