Add text annotation on scatterplot

This post provides several examples with reproducible code showing how to use text() function of matplotlib to add text annotations on the plot.

Basic scatterplot

You can create a basic scatterplot using regplot() function of seaborn library. The following parameters should be provided:

data : dataset
x : positions of points on the X axis
y : positions of points on the Y axis
fit_reg : if True, show the linear regression fit line
marker : marker shape
color : the color of markers

import pandas as pd
import numpy as np
import matplotlib.pylab as plt
import seaborn as sns
 
# Create dataframe
df = pd.DataFrame({
'x': [1, 1.5, 3, 4, 5],
'y': [5, 15, 5, 10, 2],
'group': ['A','other group','B','C','D']
})
 
sns.scatterplot(data=df, x="x", y="y", s=200)

plt.show()

Add one annotation

Once you have created the dataset and plotted the scatterplot with the previous code, you can use text() function of matplotlib to add annotation. The following parameters should be provided:

x : the position to place the text in x axis
y : the position to place the text in y axis
s: the text

You can also specify the additional parameters such as horizontalalignment, size, color, weight to design your text.

import pandas as pd
import numpy as np
import matplotlib.pylab as plt
import seaborn as sns
 
# Create dataframe
df = pd.DataFrame({
'x': [1, 1.5, 3, 4, 5],
'y': [5, 15, 5, 10, 2],
'group': ['A','other group','B','C','D']
})
 
sns.scatterplot(data=df, x="x", y="y", s=200)
plt.text(x=1.7, y=15, s="A", weight="bold")

plt.show()

Use a loop to annotate each marker

If you want to annotate every markers, it is practical to use a loop as follow:

import pandas as pd
import numpy as np
import matplotlib.pylab as plt
import seaborn as sns
 
# Create dataframe
df = pd.DataFrame({
'x': [1, 1.5, 3, 4, 5],
'y': [5, 15, 5, 10, 2],
'group': ['A','other group','B','C','D']
})
 
sns.scatterplot(data=df, x="x", y="y", s=200)

# add annotations one by one with a loop
for line in range(0,df.shape[0]):
     plt.text(
          df["x"][line]+0.2,
          df["y"][line],
          df["group"][line],
          ha='left',
          weight='bold'
     )

plt.show()

Going further

This post explains how to customize the appearance of the markers in a scatter plot with seaborn.

Contact & Edit

👋 This document is a work by Yan Holtz. You can contribute on github, send me a feedback on twitter or subscribe to the newsletter to know when new examples are published! 🔥