Plotting circles

[joleroi]

Example for plotting astropy.regions

@keflavich, @astrofrog

• I don't know what API you had in mind (to_mpl()/plot() on each object vs. object_to_mpl(region)
• I don't know how you want to do the plotting (transformation to pixels in astropy.regions then convert to patch vs. let matplotlib do the conversion (like I did for now) downside - always have to create wcsaxis instance)

To run an example go to regions/plotting and run

python plotting.py

[keflavich]

you could just use the region class directly, rather than the string name of the class

[keflavich]

For API, I like to_mpl_patch for single regions, and to_mpl_patchcollection for multiple regions. It would be nice if we could have some sort of overloading that would allow matplotlib.pyplot.plot(region), but that is probably unrealistic. However, supporting matplotlib.axes.Axes.add_artist should be possible.

[astrofrog]

+1 to to_mpl_patch and to_mpl_patchcollection

[joleroi]

What about plotting SkyRegions? Ok to use WCSaxis?

[keflavich]

yes, that's the right thing to do in examples, but that doesn't need to be part of the API (as long as the API is readily usable with wcsaxes)

[joleroi]

I don't understand. Let met explain my problem again. This is how it's done in gammapy

def to_mpl_artist(self, ax, **kwargs):
        """Convert to mpl patch using a given wcs transformation
        Parameters
        ----------
        ax : `~astropy.wcsaxes.WCSAxes`
            WCS axis object
        kwargs : dict
            kwargs are forwarded to mpatches.Circle
        Returns
        -------
        patch : `~matplotlib.mpatches.Circle`
            Matplotlib patch object
        """

        import matplotlib.patches as mpatches

        val = self.pos.galactic
        center = (val.l.value, val.b.value)

        temp = dict(transform=ax.get_transform('galactic'),
                    radius=self.radius.value)
        kwargs.update(temp)
        patch = mpatches.Circle(center, **kwargs)

        return patch

So the WCSaxis is actually part of the API. My question is basically if I can copy&paste this function to astropy/regions or if we want to come up with another solution.

[keflavich]

I understand better now. For now, yes, go with that. I'm not sure if there's a non-wcs-axis way to get the transforms easily.

[astrofrog]

This looks great! Using WCSAxes sounds good to me.

[joleroi]

I changed the API and added a basic test

[keflavich]

OK, will review.

[keflavich]

@joleroi say if you think this is ready to merge, or merge it yourself if you'd like. Others (@cdeil, @astrofrog, myself) are starting to hack on other aspects of the code. It would be nice to have this merged, but would also be nice to have it merged with passing tests.

[coveralls]

Changes Unknown when pulling 7a2f152 on joleroi:ploting into * on astropy:master*.