remove colorbar from figure in matplotlib


Question

This should be easy but I'm having a hard time with it. Basically, I have a subplot in matplotlib that I'm drawing a hexbin plot in every time a function is called, but every time I call the function I get a new colorbar, so what I'd really like to do is update the colorbar. Unfortunately, this doesn't seem to work since the object the colorbar is attached to is being recreated by subplot.hexbin.

def foo(self):
   self.subplot.clear()
   hb = self.subplot.hexbin(...)
   if self.cb:
      self.cb.update_bruteforce() # Doesn't work (hb is new)
   else:
      self.cb = self.figure.colorbar(hb)

I'm now in this annoying place where I'm trying to delete the colorbar axes altogether and simply recreate it. Unfortunately, when I delete the colorbar axes, the subplot axes don't reclaim the space, and calling self.subplot.reset_position() isn't doing what I thought it would.

def foo(self):
   self.subplot.clear()
   hb = self.subplot.hexbin(...)
   if self.cb:
      self.figure.delaxes(self.figure.axes[1])
      del self.cb
      # TODO: resize self.subplot so it fills the 
      #    whole figure before adding the new colorbar
   self.cb = self.figure.colorbar(hb)

Does anyone have any suggestions?

Much appreciated! Adam

1
23
3/10/2011 4:55:03 PM

Accepted Answer

Alright, here's my solution. Not terribly elegant, but not a terrible hack either.

def foo(self):
   self.subplot.clear()
   hb = self.subplot.hexbin(...)
   if self.cb:
      self.figure.delaxes(self.figure.axes[1])
      self.figure.subplots_adjust(right=0.90)  #default right padding
   self.cb = self.figure.colorbar(hb)

This works for my needs since I only ever have a single subplot. People who run into the same problem when using multiple subplots or when drawing the colorbar in a different position will need to tweak.

10
3/10/2011 8:37:14 PM

I think the problem is that with del you cancel the variable, but not the referenced object colorbar. If you want the colorbar to be removed from plot and disappear, you have to use the method remove of the colorbar instance and to do this you need to have the colorbar in a variable, for which you have two options:

  1. holding the colorbar in a value at the moment of creation, as shown in other answers e.g. cb=plt.colorbar()
  2. retrieve an existing colorbar, that you can do following (and upvoting :)) what I wrote here: How to retrieve colorbar instance from figure in matplotlib then:

cb.remove() plt.draw() #update plot


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