Use error bars in a Matplotlib scatter plot

Prerequisites: Matplotlib

In this article, we will create a scatter plot with error bars using Matplotlib. Error bar charts are a great way to represent the variability in your data. It can be applied to graphs to provide an additional layer of detailed information on the presented data. 

Approach

• Import required python library.
• Create data.
• Pass required values to errorbar() function
• Plot graph.

Syntax: matplotlib.pyplot.errorbar(x, y, yerr=None, xerr=None, fmt=”, ecolor=None, elinewidth=None, capsize=None, barsabove=False, lolims=False, uplims=False, xlolims=False, xuplims=False, errorevery=1, capthick=None, \*, data=None, \*\*kwargs)

Parameters: This method accept the following parameters that are described below:

• x, y: These parameters are the horizontal and vertical coordinates of the data points.
• fmt: This parameter is an optional parameter and it contains the string value.
• capsize: This parameter is also an optional parameter. And it is the length of the error bar caps in points with default value NONE.

Implementation of the concept discussed above is given below:

Example 1: Adding Some error in a ‘y’ value.

Python3

import matplotlib.pyplot as plt

a = [1, 3, 5, 7]
b = [11, -2, 4, 19]
plt.scatter(a, b)

c = [1, 3, 2, 1]

plt.errorbar(a, b, yerr=c, fmt="o")
plt.show()

Output:

Example 2: Adding Some errors in the ‘x’ value.

Python3

import matplotlib.pyplot as plt

a = [1, 3, 5, 7]
b = [11, -2, 4, 19]
plt.scatter(a, b)

c = [1, 3, 2, 1]

plt.errorbar(a, b, xerr=c, fmt="o")
plt.show()

Output:

Example 3: Adding error in x & y

Python3

import matplotlib.pyplot as plt

a = [1, 3, 5, 7]
b = [11, -2, 4, 19]
plt.scatter(a, b)


c = [1, 3, 2, 1]
d = [1, 3, 2, 1]

# you can use color ="r" for red or skip to default as blue
plt.errorbar(a, b, xerr=c, yerr=d, fmt="o", color="r")

plt.show()

Output:

Example 4: Adding variable error in x and y.

Python3

# importing matplotlib
import matplotlib.pyplot as plt


# making a simple plot
x = [1, 2, 3, 4, 5]
y = [1, 2, 1, 2, 1]

# creating error
y_errormin = [0.1, 0.5, 0.9,
              0.1, 0.9]
y_errormax = [0.2, 0.4, 0.6,
              0.4, 0.2]

x_error = 0.5
y_error = [y_errormin, y_errormax]

# plotting graph
# plt.plot(x, y)
plt.errorbar(x, y,
             yerr=y_error,
             xerr=x_error,
             fmt='o')
plt.show()

Output: