Shift error bars in seaborn barplot with two categories?-CodePudding

The

CodePudding user response：

You plot categorical values (the x values are strings), the x positions of the (center of the) bar groups and the error bars the way you plotted them are range(n) where n is the number of parameters. These x positions can also be retrieved by ax.xaxis.get_majorticklocs().

To put the error bars in the middle of the bar you need to consider the offset of each bar relative to the center of the bar group. This offset depends on the bar width (default is 0.8) and the number of bars per group. For a generic solution you'll to differentiate between odd and even numbers of bars per group.

The following shows the case for 2 hues or bars per group (df['Sobol index'].nunique() == 2):

# Plot width = 0.8 grid = sns.catplot(data=df, x="Parameter", y="Value", col="Output", col_wrap=2, hue="Sobol index", kind="bar", aspect=1.8, legend_out=False, width=width) # Add error lines and values for ax, var in zip(grid.axes.ravel(), ["P", "D", "I", "N"]): # Error bars ticklocs = ax.xaxis.get_majorticklocs() offset = 0.5 * width / 2 # 2 = number of hues or bars per group ax.errorbar(x=np.append(ticklocs - offset, ticklocs offset), y=df[df["Output"] == var]["Value"], yerr=err_df[err_df["Output"] == var]["value"], ecolor='black', linewidth=0, capsize=2, elinewidth=1) # Value labels for c in ax.containers: if type(c) == matplotlib.container.BarContainer: ax.bar_label(c, labels=[f'{v.get_height():.2f}' if v.get_height() >= 0.01 else "<0.01" for v in c], label_type='edge') grid.tight_layout()