Bar Charts (matplotlib)

🟨🐍 Technique Card: Bar Charts using matplotlib (practical)

💡 What This Lets You Do

Create simple bar charts to visually compare data. Great for showing totals, categories, and differences.

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🧰 You'll Need

• Python installed
• matplotlib installed (pip install matplotlib if needed)

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🪄 Code Example: A Simple Bar Chart

import matplotlib.pyplot as plt

# Data
categories = ["Apples", "Bananas", "Cherries"]
quantities = [10, 15, 7]

# Create bar chart
plt.bar(categories, quantities)

# Add labels
plt.title("Fruit Sold Today")
plt.xlabel("Fruit")
plt.ylabel("Quantity")

# Show chart
plt.show()

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🔍 Key Parts Explained

Code	What It Does
import matplotlib.pyplot as plt	Brings in the chart-making tools
plt.bar()	Makes a bar chart
plt.title(), xlabel(), ylabel()	Adds labels
plt.show()	Displays the chart in a window or output cell

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🛠️ Try This

Change the values in categories and quantities to match your own data (like food miles, recycling totals, etc.).

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🎯 Mini Challenges

1. Create a bar chart showing how many children cycle, walk, or drive to school.
2. Try changing the colours using color=["red", "yellow", "pink"].
3. Sort your data so the tallest bar is first.

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📊 Using Data from a CSV with Pandas and Plotting with Matplotlib

You can load data from a .csv file using pandas, then select the columns you want to plot and assign them to x and y variables for clarity.

🧪 Example Code

import pandas as pd
import matplotlib.pyplot as plt

# Read data from a CSV file
df = pd.read_csv("fruit_sales.csv")

# Prepare x and y data from specific columns in the DataFrame
x = df["Fruit"]
y = df["Sold"]

# Create a bar chart
plt.bar(x, y)

# Add labels and a title
plt.title("Fruit Sold Today")
plt.xlabel("Fruit")
plt.ylabel("Quantity")
plt.show()

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📁 Example CSV File (fruit_sales.csv)

Fruit	Sold
Apples	12
Bananas	18
Oranges	9

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✅ Tips

• Make sure your .csv file is saved in the same folder as your Python script, or provide the full path to the file.
• Your column names in the .csv must match exactly what you type in your code ("Fruit" and "Sold" in this example).

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🔗 Linked Cards

• 🐍 Technique Card: Reading CSV Files with Pandas (practical)
• 📊 Technique Card: Working With CSV Files (practical)
• 📊 Technique Card: Percentages (deeper)
• 📊 Technique Card: Telling Stories With Data (deeper)

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📹 Video Link - Basic Bar Charts

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📹 Video Link - Real World Data

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