Types of Plots in Matplotlib

Types of Plots in Matplotlib

• There are three important types of graphs that can be plotted using Matplotlib. These are

1) Bar graphs

• The bar graph makes use of bars to represent the data. The bar() function is used for this purpose.

Syntax

ax.bar(x, height, width, bottom, align)

Parameters

• x: This parameter is used to represent a sequence of scalar values that represents the x coordinates of the bars. The align parameter controls if x is the bar center (default) or left edge.

•  height: This parameter is either a scalar or sequence of scalar values representing the height(s) of the bars which makes the y‒axis value.

•  width: This parameter is either a scalar or array‒like and it is optional. The default value of this parameter is 0.8.

• bottom: This is also a scalar or array‒like and it is optional. The default value is None.

•  align: The values of this parameter are {'center', 'edge'}, optional and the default value of this parameter is 'center'.

Example

• Following program displays simple bar chart.

In [17]: from matplotlib import pyplot as plt

import numpy as np

x = np.array(["one", "two", "three", "four"])

y = np.array([7,4,15,10])

plt.bar(x,y)

plt.show()

Output

• If we want to draw horizontal bar graph, we use barh() function. For instance ‒

from matplotlib import pyplot as plt

import numpy as np

x = np.array(["one", "two","three", "four"])

y = np.array([7,4,15,10])

plt.barh(x,y)

plt.show()

Output

2) Histogram

•  The histogram is used to understand the distribution of a continuous numerical variable. A histogram is a graph showing frequency distributions. It is a graph showing the number of observations within each given interval.

•  For example ‒ To represent the weights of 1000 people we may use histogram.

• Using Matplotlib, we can draw the histogram using the function hist() function. The hist() function will use an array of numbers as data to create a histogram, the array is sent into the function as an argument.

• A histogram shows the frequency on the vertical axis and the horizontal axis is another dimension. Usually it has bins, where every bin has a minimum and maximum value. Each bin also has a frequency between data and infinite.

• For example ‒

In [9]: from matplotlib import pyplot as plt

import numpy as np

data = np.random.randn(1000)

plt.hist(data, bins=20)

plt.show()

Output

3) Scatter plots

• Scatter plots are used to represent values for two different numeric variables. The scatter() function plots one dot for each observation. It needs two arrays of the same length, one for the values of the x‒axis and one for values on the y‒axis.

• For example ‒ Following is a plot of 10 people of different age group who have different weights in kgs.

In [12]: from matplotlib import pyplot as plt

import numpy as np

age = np.array([10,22,35,50,40,3,65,54,29,70])

weight = np.array([20,60,75,90,55,8,65,100,64,46])

plt.scatter(age, weight)

plt.show()

Output

4) Pie chart

•  The pie chart can be created using the function pie() is used.

•  For example ‒

In [8]: from matplotlib import pyplot as plt

import numpy

data = [20,30,35,5,10]

plt.pie(data)

plt.show()

Output

• By default the plotting of the first wedge starts from the x‒axis and moves counterclockwise, Hence the data is plotted as follows –

• We can also label the elements of pie chart. The code is as follows –

from matplotlib import pyplot as plt

import numpy

data = [20,30,35,5,10]

1 = ["OPPO","OnePlus","Samsung", "Apple", "Vivo"]

plt.pie(data,labels = 1)

plt.show()

Output

•  We can display the percentage data in the pie chart as follows –

from matplotlib import pyplot as plt

import numpy

data = [20,30,35,5,10]

1 =["OPPO","OnePlus", "Samsung", "Apple", "Vivo"]

plt.pie(data,labels = 1,autopct=%1.1f%%')

plt.show()

Output

Review Questions

1. What is Matplotlib? Enlist its feature.

2.What is the use of Pyplot in Matplotlib?

3.What are the types of plots in Matplotlib ?

4.How to create piechart in Matplotlib? Give an example.