Is there any way we label the plots in boxplot using matplotlib?

Question

Is there any way to label the outliers in a box plot. like i am plotting the prices for each drug and trying to find places with overpriced drug. so i want to label the outliers with the name of the place from where it belong. How to achieve it using matplotlib ?

Answer 1

Boxplot lets you pass an object for flierprops.

import random
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

# Mock data from the boxplot demo
spread = np.random.rand(50) * 100
center = np.ones(25) * 50
flier_high = np.random.rand(10) * 100 + 100
flier_low = np.random.rand(10) * -100
data = np.concatenate((spread, center, flier_high, flier_low))

# Set up
fig, ax = plt.subplots()

# flierprops example
red_square = dict(markerfacecolor='r', marker='s')
box = ax.boxplot(data, flierprops=red_square)

This simple sample produces:

If you want to label something, you can use plt.annotate like so:

box = ax.boxplot(data,)

top_points = box["fliers"][0].get_data()
ax.scatter(top_points[0], top_points[1], marker="o")

# Roughly based on https://stackoverflow.com/a/5147430/10553976
ax.annotate("I labeled this", xy=(top_points[0][1], top_points[1][1]),
            xytext=(-20, 20),
            textcoords='offset points', ha='right', va='bottom',
            bbox=dict(boxstyle='round,pad=0.5', fc='yellow', alpha=0.5),
            arrowprops=dict(arrowstyle = '->', connectionstyle='arc3,rad=0'))

And this sample produces: