Seaborn FacetGrid – Places a single color bar after the last subgraph
I’m trying to add color bars to the grid of 3 seaborn plots. I can add color bars to 3 separate plots or squeeze a color bar next to a third plot. I want to have a color bar after the third plot without changing the size of the last plot.
I got a lot of good ideas from this answer but couldn’t solve my exact problem: SO Question/Answer
Here is my current code :
import seaborn as sns
def masked_vs_unmasked_facets(output_dir, merged_df, target_col, thresholds):
# defining the maximal values, to make the plot square
z_min = merged_df[['z_full', 'z_masked']].min(axis=0, skipna=True).min(skipna=True)
z_max = merged_df[['z_full', 'z_masked']].max(axis=0, skipna=True).max(skipna=True)
z_range_value = max(abs(z_min), abs(z_max))
# Setting the column values to create the facet grid
for i, val in enumerate(thresholds):
merged_df.loc[merged_df.info_score_masked > val, 'PlotSet'] = i
# Start the actual plots
g = sns. FacetGrid(merged_df, col='PlotSet', size=8)
def facet_scatter(x, y, c, **kwargs):
kwargs.pop("color")
plt.scatter(x, y, c=c, **kwargs)
# plt.colorbar() for multiple colourbars
vmin, vmax = 0, 1
norm=plt. Normalize(vmin=vmin, vmax=vmax)
g = (g.map(facet_scatter, 'z_full', 'z_masked', 'info_score_masked', norm=norm, cmap='viridis'))
ax = g.axes[0]
for ax in ax:
ax.set_xlim([-z_range_value * 1.1, z_range_value * 1.1])
ax.set_ylim([-z_range_value * 1.1, z_range_value * 1.1])
ax.plot(ax.get_xlim(), ax.get_ylim(), ls="--", c=".3")
plt.colorbar() # Single squashed colorbar
plt.show()
masked_vs_unmasked_facets(output_dir, masking_results, 'info_score_masked', [0, 0.7, 0.9])
Single color bar, but the 3rd figure is flattened
Multiple color bars, but crowded
Solution
Following @ImportanceOfBeingEarnest’s suggestion, I found that I needed to add another set of axes to the polygon grid and then assign those axes to the color bar. To save this extra element to the drawing, I used bbox_extra_artist
kwarg as a tight bounding box. Another small addition is a small clause for capturing edge cases where one aspect of me has no data. In this case, I append a blank row with one category instance, so each category always has at least 1 row.
import seaborn as sns
def masked_vs_unmasked_facets(output_dir, merged_df, target_col, thresholds):
z_min = merged_df[['z_full', 'z_masked']].min(axis=0, skipna=True).min(skipna=True)
z_max = merged_df[['z_full', 'z_masked']].max(axis=0, skipna=True).max(skipna=True)
z_range_value = max(abs(z_min), abs(z_max))
for i, val in enumerate(thresholds):
merged_df.loc[merged_df.info_score_masked > val, 'PlotSet'] = i
# Catch instances where there are no values in category, to ensure all facets are drawn each time
if i not in merged_df['PlotSet'].unique():
dummy_row = pd. DataFrame(columns=merged_df.columns, data={'PlotSet': [i]})
merged_df = merged_df.append(dummy_row)
g = sns. FacetGrid(merged_df, col='PlotSet', size=8)
def facet_scatter(x, y, c, **kwargs):
kwargs.pop("color")
plt.scatter(x, y, c=c, **kwargs)
vmin, vmax = 0, 1
norm=plt. Normalize(vmin=vmin, vmax=vmax)
g = (g.map(facet_scatter, 'z_full', 'z_masked', 'info_score_masked', norm=norm, cmap='viridis'))
titles = ["Correlation for all masked / unmasked z-score with {} above {}".format(target_col, threshold) for threshold in thresholds]
axs = g.axes.flatten()
for i, ax in enumerate(axs):
ax.set_title(titles[i])
ax.set_xlim([-z_range_value * 1.1, z_range_value * 1.1])
ax.set_ylim([-z_range_value * 1.1, z_range_value * 1.1])
ax.plot(ax.get_xlim(), ax.get_ylim(), ls="--", c=".3")
cbar_ax = g.fig.add_axes([1.015,0.13, 0.015, 0.8])
plt.colorbar(cax=cbar_ax)
# extra_artists used here
plt.savefig(os.path.join(output_dir, 'masked_vs_unmasked_scatter_final.png'), bbox_extra_artists=(cbar_ax,), bbox_inches='tight')
masked_vs_unmasked_facets(output_dir, masking_results, 'info_score_masked', [0, 0.7, 0.9])
This gave me: