Add colorbar to existing axis

Question

I m making some interactive plots and I would like to add a colorbar legend  I don t want the colorbar to be in its own axes  so I want to add it to the existing axes  I m having difficulties doing this  as most of the example code I have found creates a new axes for the colorbar    I have tried the following code using matplotlib colorbar ColorbarBase  which adds a colorbar to an existing axes  but it gives me strange results and I can t figure out how to specify attributes of the colorbar  for instance  where on the axes it is placed and what size it is   import matplotlib import matplotlib pyplot as plt from matplotlib cm import coolwarm import numpy as np  x   np random uniform 1  10  10  y   np random uniform 1  10  10  v   np random uniform 1  10  10   fig  ax   plt subplots    s   ax scatter x  y  c v  cmap coolwarm   matplotlib colorbar ColorbarBase ax ax  cmap coolwarm  values sorted v                                    orientation  horizontal     Using fig colorbar instead ofmatplotlib colorbar ColorbarBase still doesn t give me quite what I want  and I still don t know how to adjust the attributes of the colorbar   fig colorbar s  ax ax  cax ax      Let s say I want to have the colorbar in the top left corner  stretching about halfway across the top of the plot  How would I go about doing that   Am I better off writing a custom function for this  maybe using LineCollection

User · Answer

This technique is usually used for multiple axis in a figure. In this context it is often required to have a colorbar that corresponds in size with the result from imshow. This can be achieved easily with the axes grid tool kit:

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import make_axes_locatable

data = np.arange(100, 0, -1).reshape(10, 10)

fig, ax = plt.subplots()
divider = make_axes_locatable(ax)
cax = divider.append_axes('right', size='5%', pad=0.05)

im = ax.imshow(data, cmap='bone')

fig.colorbar(im, cax=cax, orientation='vertical')
plt.show()

User · Answer

The colorbar has to have its own axes   However  you can create an axes that overlaps with the previous one   Then use the cax kwarg to tell fig colorbar to use the new axes   For example   import numpy as np import matplotlib pyplot as plt  data   np arange 100  0  -1  reshape 10  10   fig  ax   plt subplots   cax   fig add axes  0 27  0 8  0 5  0 05    im   ax imshow data  cmap  gist earth   fig colorbar im  cax cax  orientation  horizontal   plt show

User · Answer

Couldn t add this as a comment  but in case anyone is interested in using the accepted answer with subplots  the divider should be formed on specific axes object  rather than on the numpy ndarray returned from plt subplots   import numpy as np import matplotlib pyplot as plt from mpl toolkits axes grid1 import make axes locatable data   np arange 100  0  -1  reshape 10  10  fig  ax   plt subplots ncols 2  nrows 2  for row in ax      for col in row          im   col imshow data  cmap  bone           divider   make axes locatable col          cax   divider append axes  right   size  5    pad 0 05          fig colorbar im  cax cax  orientation  vertical   plt show

[python] Add colorbar to existing axis

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