Python

5 Examples Of Best Python Graphs

Anyone attempting to uncover and convey insights from data needs to be proficient in data visualization. Visualization is essential to the machine learning process at every stage of analysis. Python is frequently used for plotting graphs because it is one of the most important programming languages in this area. Thus, programming the creation of graphics is a very common task today. Python4Delphi’s Matplotlib or Seaborn libraries make it simple to resolve (P4D) and make the best Python graphs. Thus, in this article, we will look at the top 5 Python graph examples using the best data visualization tools Python has to offer.

What is a Barplot?

5 Examples Of Best Python Graphs - an image of a laptop showing a bar chart

A bar plot is used to display categorical data. Categorical data are displayed as rectangular bars with heights proportional to the values they represent in a bar plot. Moreover, it is frequently used to compare the values of various data categories using various data visualization tools Python.

What is categorical data?

A categorical data set is nothing more than grouping data into various logical categories, such as tall, medium, short, etc., for data on a person’s height. You must figure out the number of each category to create a bar plot.

Users must first install all of the necessary libraries we will use. Python’s pip command is used to accomplish this. Importing these packages should then be the first step in your script.

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

Let’s make a dataset with 10 distinct categories and give each one a value.

Use the np.random.randn() function generates a random array, passing it the array’s size, upper and lower bounds as arguments.

# create data
x = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J']
y = np.random.randint(low=0, high=90, size=10)
print(y)

Here is the output of the program:

[47, 0, 27,  23, 42,  4, 46, 76, 33, 71]

As you can see, the output y contains an array of values that were chosen at random. We then use the plt.bar() function passing the two arguments x value and y value, to plot a barplot in Matplotlib:

# simple bar chart
plt.bar(x, y)
plt.xlabel("Categories")
plt.ylabel("Values")
plt.title("Bar plot of categories')
plt.show()

Matplotlib is a powerful Python library that you can use in various applications and is the basis for many other Python libraries. Check out this article to learn how to make 2d graphs with Matplotlib.

What is a line plot?

5 Examples Of Best Python Graphs - an image of a laptop with a stacked line graph on the screen

An informational chart known as a line plot shows data as a series of data points connected by straight line segments.

Line plots are one of the most frequently used charts that show how one or more data points have changed direction over time. For example, dateTime would be the x-axis in this instance, and the measured quantity, such as stock price, weather, monthly sales, etc., would be on the y-axis. A line plot is frequently the first option when displaying any time series data.

We will first import the packages needed to make line plots. These imports will be the same as the ones we just saw for bar plots.

Let’s use the np.linspace() function to create a dataset with 50 values between 1 and 100. This will appear on the x-axis, and the log of x will appear on the y-axis.

Using plt.plot, the line graph of y against x is produced (x,y). It connects every point in a straight line:

# simple line plot
x = np.linspace(1,100,5)
y = np.log(x)
plt.plot(x, y)
plt.xlabel('x')
plt.ylabel('logx')
plt.title('Basic line plot')
plt.xlim(0,100)
plt.ylim(0,5)plt.show()

How can you create a pie chart in Python?

5 Examples Of Best Python Graphs - an image of the PyScripter Python IDE

The pie chart displays the data distribution based on the percentage of the pie that is occupied. After making the necessary imports, the plt.pie() command in Python can be used to plot a pie chart.

Let’s see a simple example:

import matplotlib.pyplot as plt
import numpy as np

y = np.array([45, 15, 25, 15])
labels = ["Peaches", "Bananas", "Cherries", "Apricots"]

plt.pie(y, labels=labels)
plt.show()

Why are scatter plots one of the best Python graphs?

5 Examples Of Best Python Graphs - the Delphi VCL and Delphi FMX Python GUI library download page

You can graph two data sets along two axes to create a scatter plot. It helps to depict how the two variables are related to one another.

A positive (or negative) linear relationship may exist if the value on the y-axis appears to rise as the x-axis rises (or falls). In contrast, if the points are randomly spaced out without any discernible pattern, it might suggest that there is no dependent relationship.

The scatterplot in Python Matplotlib can be made using either pyplot.plot() or pyplot.scatter(). With the aid of these features, you can enhance your scatter plot by altering the points’ size, color, or shape.

Therefore, the question of what distinguishes plt.scatter() from plt.plot() frequently arises. With pyplot.plot(), any property you apply (color, shape, or size of points) will be applied to all of the points, whereas with pyplot.scatter(); you have more control over how each point looks.

In other words, you can use plt.scatter() to make each dot (datapointcolor, ) ‘s shape and size depend on a different variable—the same variable, or even (y). In contrast, the properties you set when using pyplot.plot() will be applied to every point in the chart.

The same imports we made earlier for numpy, pandas, and matplotlib are required here. First, let’s generate fictitious data with the np.random.randint() function. You must state how many points you need for the arguments. Additionally, you can specify the required random variable’s lower and upper bounds.

Then, employ Matplotlib’s plt.scatter() function to create a scatter plot. The variables x and y must be given as arguments.

# simple scatterplot
x = range(50)
y = range(50) + np.random.randint(0, 30, 50)
plt.scatter(x, y)
plt.title('Basic scatter plot')
plt.xlabel('X value')
plt.ylabel('Y value')
plt.show()

What is a heat map? Does it qualify as one of the best Python graphs?

5 Examples Of Best Python Graphs - a screen with a collection of different Python graphs

Multivariate data graphically represented as a matrix of columns and rows is known as a heat map. Heat maps are a very helpful tool when describing the correlation between several numerical variables and displaying patterns and anomalies.

What is meant by correlation?

The degree of a variable’s relationship with other variables is measured by its correlation, a dimensionless unit. It gauges the linear relationship between variables’ strength and direction. Its value, which ranges from 0 to 1, represents strength, and the + and – signs, represent direction.

The values used in the heatmap plot below were generated randomly using NumPy. Although there are many possible parameters, we will concentrate on the fundamental plot here.

import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt

np.random.seed(0)
sns.set()
uniform_data = np.random.rand(10, 12)
ax = sns.heatmap(uniform_data, vmin=0, vmax=1)
plt.show()

Seaborn is a user-friendly library offering strong tools for creating better and more beautiful visualizations. In addition, users can modify the Seaborn plots to meet individual needs and can use Python to create heatmaps for various applications. Check out this article to learn more about how you can use these libraries with real-wold data.

Can you plot these best Python graphs?

5 Examples Of Best Python Graphs - a person looking at a laptop held in their hands. The screen shows the Python4Delphi project page.

A free set of components called Python for Delphi (P4D) integrates the Python DLL into Delphi and Lazarus (FPC). P4D makes it simple to run Python scripts and develop new Python modules and types. For example, you can use the Matplotlib library or send the data to Delphi and create the chart if you already have a Python application and need to create charts. You can also produce this chart using Matplotlib and then show in the Delphi Windows GUI application.

You can use Python4Delphi in a number of different ways, such as:

  • Create a Windows GUI around your existing Python app.
  • Add Python scripting to your Delphi Windows apps.
  • Add parallel processing to your Python apps through Delphi threads.
  • Enhance your speed-sensitive Python apps with functions from Delphi for more speed.

Now that you know how to plot the five best Python graphs, you can start doing data visualizations of your own using Python libraries and P4D! 

 

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