Before-after comparison plots in Matplotlib - Mini Project: Build & Apply

Before-After Comparison Plots

📖 Scenario: You work in a health clinic. You want to compare patients' blood pressure before and after a treatment.

🎯 Goal: Create a simple plot that shows blood pressure values before and after treatment for each patient. This helps to see if the treatment worked.

📋 What You'll Learn

Create a dictionary with patient names and their blood pressure before treatment

Create a dictionary with patient names and their blood pressure after treatment

Use matplotlib to plot before and after values side by side for each patient

Label the plot clearly with title, axis labels, and legend

💡 Why This Matters

🌍 Real World

Before-after comparison plots are used in health, marketing, and many fields to show changes clearly.

💼 Career

Data scientists often create comparison plots to communicate results of experiments or treatments.

1

Create blood pressure data dictionaries

Create a dictionary called bp_before with these exact entries: 'Anna': 140, 'Ben': 130, 'Cara': 150, 'Dan': 135. Then create another dictionary called bp_after with these exact entries: 'Anna': 130, 'Ben': 125, 'Cara': 140, 'Dan': 128.

Matplotlib

# Create the bp_before and bp_after dictionaries with exact values
# Your code here

Need a hint?

Use curly braces {} to create dictionaries with the exact patient names and values.

2

Prepare patient names list for plotting

Create a list called patients that contains the patient names in this exact order: 'Anna', 'Ben', 'Cara', 'Dan'.

Matplotlib

bp_before = {'Anna': 140, 'Ben': 130, 'Cara': 150, 'Dan': 135}
bp_after = {'Anna': 130, 'Ben': 125, 'Cara': 140, 'Dan': 128}
# Create the patients list with exact names in order
# Your code here

Need a hint?

Use square brackets [] to create a list with the patient names in the given order.

3

Plot before and after blood pressure values

Import matplotlib.pyplot as plt. Create two lists called before_values and after_values that contain the blood pressure values from bp_before and bp_after for each patient in patients. Then use plt.bar to plot the before values shifted left by 0.2 and after values shifted right by 0.2 on the x-axis positions. Use patients as x-axis labels.

Matplotlib

bp_before = {'Anna': 140, 'Ben': 130, 'Cara': 150, 'Dan': 135}
bp_after = {'Anna': 130, 'Ben': 125, 'Cara': 140, 'Dan': 128}
patients = ['Anna', 'Ben', 'Cara', 'Dan']
# Import matplotlib.pyplot as plt
# Create before_values and after_values lists
# Plot bars for before and after values with shifts
# Your code here

Need a hint?

Use list comprehension to get values for each patient. Use plt.bar twice with shifted x positions for before and after bars.

4

Add labels and show the plot

Add a title 'Blood Pressure Before and After Treatment' using plt.title. Label the x-axis as 'Patients' and y-axis as 'Blood Pressure' using plt.xlabel and plt.ylabel. Add a legend with plt.legend(). Set the x-axis ticks to range(len(patients)) with labels patients using plt.xticks. Finally, display the plot with plt.show(). This will show the before and after blood pressure comparison clearly.

Matplotlib

import matplotlib.pyplot as plt

bp_before = {'Anna': 140, 'Ben': 130, 'Cara': 150, 'Dan': 135}
bp_after = {'Anna': 130, 'Ben': 125, 'Cara': 140, 'Dan': 128}
patients = ['Anna', 'Ben', 'Cara', 'Dan']

before_values = [bp_before[patient] for patient in patients]
after_values = [bp_after[patient] for patient in patients]

x = range(len(patients))
plt.bar([pos - 0.2 for pos in x], before_values, width=0.4, label='Before')
plt.bar([pos + 0.2 for pos in x], after_values, width=0.4, label='After')
# Add title, axis labels, legend, x-ticks, and show the plot
# Your code here

Need a hint?

Use plt.title, plt.xlabel, plt.ylabel, plt.legend, plt.xticks, and plt.show to complete the plot.