matplotlib-devel

[matplotlib-devel] Completely wrong tick formatting

[Pål G. E. <pa...@gm...>]

Hi

I'm having some problems with the formatter of ticks in a polar plot.
Below is a minimum example
The first figure is correct, the second has wrong ticks.

This has be tested both on 1.2.0 and the latest from git (1.4.x, commit
64cc3416396ffb2811af80fc810ed63572df71d9 )

Does anyone know whys this happens?
Is it a bug in MaxNLocator

Kind regards

Pål

---------------------------
#!/usr/bin/env python

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.ticker import MaxNLocator

# Data
M=np.sin(np.meshgrid(np.arange(30),np.arange(30)))
M=np.squeeze(M[0,:,:])
Radius=np.arange(30)
Theta=np.arange(30)

# Plotting the correct figure
print('Correct ticks')
fig=plt.figure()
ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
c = ax1.pcolormesh(Theta, Radius, M)
ax1.set_frame_on(False)
plt.xticks([])
plt.yticks([])
ax2=fig.add_axes([0.9,0.1,0.05,0.7])
cb=fig.colorbar(c,cax=ax2)
plt.show()

# Doing the same plot
print('Wrong ticks by using formatter')
fig=plt.figure()
ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
c = ax1.pcolormesh(Theta, Radius, M)
ax1.set_frame_on(False)
plt.xticks([])
plt.yticks([])
ax2=fig.add_axes([0.9,0.1,0.05,0.7])
cb=fig.colorbar(c,cax=ax2)

# except now setting a limit to the number of ticks using a formatter
# which results in wrong ticks
cb.ax.yaxis.set_major_locator(MaxNLocator(3))
plt.show()
-----------------------

Re: [matplotlib-devel] Completely wrong tick formatting

[Eric F. <ef...@ha...>]

On 2013/07/04 11:43 PM, Pål Gunnar Ellingsen wrote:
> Hi
>
> I'm having some problems with the formatter of ticks in a polar plot.
> Below is a minimum example
> The first figure is correct, the second has wrong ticks.
>
> This has be tested both on 1.2.0 and the latest from git (1.4.x, commit
> 64cc3416396ffb2811af80fc810ed63572df71d9 )
>
> Does anyone know whys this happens?
> Is it a bug in MaxNLocator

No, it is a misunderstanding of how the colorbar works.  It's long axis 
is using its own units, and it maps the color scale to those units. 
Therefore, one should not try to manipulate the axis properties 
directly.  Below I show two altered lines and one deletion.  I think 
this will produce what you want.

>
> Kind regards
>
> Pål
>
> ---------------------------
> #!/usr/bin/env python
>
> import numpy as np
> import matplotlib.pyplot as plt
> from matplotlib.ticker import MaxNLocator
>
> # Data
> M=np.sin(np.meshgrid(np.arange(30),np.arange(30)))
> M=np.squeeze(M[0,:,:])
> Radius=np.arange(30)
> Theta=np.arange(30)
>
> # Plotting the correct figure
> print('Correct ticks')
> fig=plt.figure()
> ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
> c = ax1.pcolormesh(Theta, Radius, M)
> ax1.set_frame_on(False)
> plt.xticks([])
> plt.yticks([])
> ax2=fig.add_axes([0.9,0.1,0.05,0.7])
> cb=fig.colorbar(c,cax=ax2)
> plt.show()
>
> # Doing the same plot
> print('Wrong ticks by using formatter')
> fig=plt.figure()
> ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
#> c = ax1.pcolormesh(Theta, Radius, M)

c = ax1.pcolormesh(Theta, Radius, M, vmin=-1, vmax=1)

> ax1.set_frame_on(False)
> plt.xticks([])
> plt.yticks([])
> ax2=fig.add_axes([0.9,0.1,0.05,0.7])
#> cb=fig.colorbar(c,cax=ax2)

cb = fig.colorbar(c, cax=ax2, ticks=MaxNLocator(3))

>
#> # except now setting a limit to the number of ticks using a formatter
#> # which results in wrong ticks
#> cb.ax.yaxis.set_major_locator(MaxNLocator(3))

> plt.show()

Eric

> -----------------------
>
>
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Re: [matplotlib-devel] Completely wrong tick formatting

[Pål G. E. <pa...@gm...>]

Hi

Thank you that solves the problem we had.
I'm sorry for posting this on the development list, it was intended for the
users list, and I somehow entered the wrong address.

Regards

Pål

On 7 July 2013 21:44, Eric Firing <ef...@ha...> wrote:

> On 2013/07/04 11:43 PM, Pål Gunnar Ellingsen wrote:
> > Hi
> >
> > I'm having some problems with the formatter of ticks in a polar plot.
> > Below is a minimum example
> > The first figure is correct, the second has wrong ticks.
> >
> > This has be tested both on 1.2.0 and the latest from git (1.4.x, commit
> > 64cc3416396ffb2811af80fc810ed63572df71d9 )
> >
> > Does anyone know whys this happens?
> > Is it a bug in MaxNLocator
>
> No, it is a misunderstanding of how the colorbar works.  It's long axis
> is using its own units, and it maps the color scale to those units.
> Therefore, one should not try to manipulate the axis properties
> directly.  Below I show two altered lines and one deletion.  I think
> this will produce what you want.
>
> >
> > Kind regards
> >
> > Pål
> >
> > ---------------------------
> > #!/usr/bin/env python
> >
> > import numpy as np
> > import matplotlib.pyplot as plt
> > from matplotlib.ticker import MaxNLocator
> >
> > # Data
> > M=np.sin(np.meshgrid(np.arange(30),np.arange(30)))
> > M=np.squeeze(M[0,:,:])
> > Radius=np.arange(30)
> > Theta=np.arange(30)
> >
> > # Plotting the correct figure
> > print('Correct ticks')
> > fig=plt.figure()
> > ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
> > c = ax1.pcolormesh(Theta, Radius, M)
> > ax1.set_frame_on(False)
> > plt.xticks([])
> > plt.yticks([])
> > ax2=fig.add_axes([0.9,0.1,0.05,0.7])
> > cb=fig.colorbar(c,cax=ax2)
> > plt.show()
> >
> > # Doing the same plot
> > print('Wrong ticks by using formatter')
> > fig=plt.figure()
> > ax1 = fig.add_axes([0,0,0.8,1],projection='polar')
> #> c = ax1.pcolormesh(Theta, Radius, M)
>
> c = ax1.pcolormesh(Theta, Radius, M, vmin=-1, vmax=1)
>
> > ax1.set_frame_on(False)
> > plt.xticks([])
> > plt.yticks([])
> > ax2=fig.add_axes([0.9,0.1,0.05,0.7])
> #> cb=fig.colorbar(c,cax=ax2)
>
> cb = fig.colorbar(c, cax=ax2, ticks=MaxNLocator(3))
>
> >
> #> # except now setting a limit to the number of ticks using a formatter
> #> # which results in wrong ticks
> #> cb.ax.yaxis.set_major_locator(MaxNLocator(3))
>
> > plt.show()
>
> Eric
>
> > -----------------------
> >
> >
> >
> ------------------------------------------------------------------------------
> > This SF.net email is sponsored by Windows:
> >
> > Build for Windows Store.
> >
> > http://p.sf.net/sfu/windows-dev2dev
> >
> >
> >
> > _______________________________________________
> > Matplotlib-devel mailing list
> > Mat...@li...
> > https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
> >
>
>
>
> ------------------------------------------------------------------------------
> This SF.net email is sponsored by Windows:
>
> Build for Windows Store.
>
> http://p.sf.net/sfu/windows-dev2dev
> _______________________________________________
> Matplotlib-devel mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
>