[Matplotlib-users] Report a possible colorbar extend bug

[Haoyu Yang]

Dear Matplotlib team,

I hope this letter finds you well.

I'm a new matplotlib so I'm not sure if it's me doing wrong or there could be a bug replated to matplotlib itself. I'm currently running Python 3.10 with Matplotlib 3.5.1. This possible bug seems to be related to some incompatibility between the "extend" argument in "plt.figure.colorbar" and ".ax.invert_yaxis()" functions. More specifically, if I just extend the max of colorbar (first figure) or just invert the y-axis of the colorbar(second figure), everything work fine. However, if I do this two at the same time, the colorbar would be inverted while the extended arrow is not(figure three).


[cid:image002.png at 01D82B54.CD991AC0][cid:image003.png at 01D82B54.CD991AC0][cid:image005.png at 01D82B54.D51B8F30]

And I here enclosed the code which I use to create the plot:
# Generate X/Y point mesh grid
    x = np.linspace(-4.5, 1.5, 400)
    y = np.linspace(-8, -2, 400)
    X, Y = np.meshgrid(x, y)
    potential, rate_determining_step = calculate_limiting_potential_from_linear_relations(X, Y, free_energy_dict)[0], calculate_limiting_potential_from_linear_relations(X, Y, free_energy_dict)[1]   # calculate limiting potential for each point on the mesh grid

    # Create backup ground volcano plot
    fig = plt.figure(figsize=[8, 6])
    background = fig.add_subplot(111)  # add sub plot

    # Add contour plot
contour = background.contourf(X, Y, potential, levels=512, cmap="rainbow")  # create filled contour (reverse rainbow)

    # Create colorbar
    cbar = fig.colorbar(contour, shrink=0.95, aspect=15, ticks=[1, 2, 3, 4])  # create colorbar (shrink/aspect for the size of the bar)
    cbar.set_label("Limiting Potential (eV)", fontsize=16)  # add label to the colorbar
    cbar.ax.tick_params(labelsize=12)  # set tick label size
    cbar.ax.invert_yaxis()  # put the colorbar upside down

Sorry I can't  send you the script and datasheet because it contents sensitive data. Thanks for your time and wishing you all the best.

Regards,
Haoyu
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