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Colors and Transparency

Colors

When bar charts were discussed, the colors of individual bars were customized. To change the color for all plots uniformly, use the color keyword argument.


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import matplotlib.pyplot as plt
import numpy as np

data_linear = np.arange(0, 11)
data_squared = data_linear ** 2
data_log = np.exp(data_linear)

# Setting the color of the first line plot
plt.plot(data_linear, label='linear function', color='red')

# Setting the color of the second line plot
plt.plot(data_squared, '-o', label='quadratic function', color='blue')

plt.xticks(data_linear)
plt.xlabel('x', loc='right')
plt.ylabel('y', loc='top', rotation=0)
plt.legend()
plt.show()

In this case, the red color was set for the first line plot, and the second one was set to blue. Unlike scatter or bar plots, which consist of multiple elements, a line plot represents a single element, so only one color can be assigned to it. For comparison, consider the following bar chart example from an earlier section:


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import matplotlib.pyplot as plt

programming_languages = ['Python', 'Java', 'C#', 'C++']
shares = [40, 30, 17, 13]

# Setting a separate color for each bar
plt.bar(programming_languages, shares, color=['b', 'green', 'red', 'yellow'])
plt.title('Percentage of users of programming languages')
plt.show()

Transparency

Another appearance parameter is alpha (transparency of the plot). Its default value is 1 (opaque), which is its maximum possible value. Basically, its possible values range from 0 to 1, where 0 makes the plot fully transparent.


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import matplotlib.pyplot as plt
import numpy as np

data_linear = np.arange(0, 11)
data_squared = data_linear ** 2

# Changing the transparency of the first line plot
plt.plot(data_linear, label='linear function', color='red', alpha=0.5)
plt.plot(data_squared, '-o', label='quadratic function', color='blue')

plt.xticks(data_linear)
plt.xlabel('x', loc='right')
plt.ylabel('y', loc='top', rotation=0)
plt.legend()
plt.show()

Using alpha=0.5 we made the plot for the linear function more transparent in order to focus more attention on the quadratic function plot. Modifying transparency is mostly used exactly for this purpose.

Task

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Set the color of the lowest bars to 'darkslateblue'.
Set the color of the middle bars to 'steelblue' (the argument should follow the label parameter).
Set the transparency of the middle bars to 0.7 (the rightmost argument).
Set the color of the top bars to 'goldenrod'.

Solution

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Section 3. Chapter 4

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Colors and Transparency

Colors

When bar charts were discussed, the colors of individual bars were customized. To change the color for all plots uniformly, use the color keyword argument.


              123456789101112131415161718
            
import matplotlib.pyplot as plt
import numpy as np

data_linear = np.arange(0, 11)
data_squared = data_linear ** 2
data_log = np.exp(data_linear)

# Setting the color of the first line plot
plt.plot(data_linear, label='linear function', color='red')

# Setting the color of the second line plot
plt.plot(data_squared, '-o', label='quadratic function', color='blue')

plt.xticks(data_linear)
plt.xlabel('x', loc='right')
plt.ylabel('y', loc='top', rotation=0)
plt.legend()
plt.show()


              123456789
            
import matplotlib.pyplot as plt

programming_languages = ['Python', 'Java', 'C#', 'C++']
shares = [40, 30, 17, 13]

# Setting a separate color for each bar
plt.bar(programming_languages, shares, color=['b', 'green', 'red', 'yellow'])
plt.title('Percentage of users of programming languages')
plt.show()

Transparency


              123456789101112131415
            
import matplotlib.pyplot as plt
import numpy as np

data_linear = np.arange(0, 11)
data_squared = data_linear ** 2

# Changing the transparency of the first line plot
plt.plot(data_linear, label='linear function', color='red', alpha=0.5)
plt.plot(data_squared, '-o', label='quadratic function', color='blue')

plt.xticks(data_linear)
plt.xlabel('x', loc='right')
plt.ylabel('y', loc='top', rotation=0)
plt.legend()
plt.show()

Task

Swipe to start coding

Set the color of the lowest bars to 'darkslateblue'.
Set the color of the middle bars to 'steelblue' (the argument should follow the label parameter).
Set the transparency of the middle bars to 0.7 (the rightmost argument).
Set the color of the top bars to 'goldenrod'.

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 3. Chapter 4

Switch to desktop for real-world practiceContinue from where you are using one of the options below