Line styles (solid, dashed, dotted) in Matplotlib - Mini Project: Build & Apply

Line styles (solid, dashed, dotted)

📖 Scenario: You are creating a simple line chart to compare three different line styles: solid, dashed, and dotted. This is useful when you want to make your charts clearer and more visually appealing.

🎯 Goal: Build a matplotlib plot that shows three lines with different line styles: solid, dashed, and dotted.

📋 What You'll Learn

Create a list of x values from 0 to 4

Create three lists of y values for each line

Use matplotlib to plot three lines with line styles: solid, dashed, and dotted

Add a legend to identify each line style

💡 Why This Matters

🌍 Real World

Line styles help distinguish different data series in charts, making reports and presentations clearer.

💼 Career

Data scientists and analysts use line styles to improve data visualization clarity and communicate insights effectively.

1

Create the data lists

Create a list called x with values [0, 1, 2, 3, 4]. Create three lists called y1, y2, and y3 with values [0, 1, 4, 9, 16], [0, 1, 2, 3, 4], and [0, 1, 8, 27, 64] respectively.

Matplotlib

# Create the x and y data lists
# Your code here

Hint

Use square brackets to create lists with the exact values given.

2

Import matplotlib and set up the plot

Import matplotlib.pyplot as plt. Create a figure and axis using plt.subplots() and store them in variables fig and ax.

Matplotlib

x = [0, 1, 2, 3, 4]
y1 = [0, 1, 4, 9, 16]
y2 = [0, 1, 2, 3, 4]
y3 = [0, 1, 8, 27, 64]

# Import matplotlib.pyplot as plt and create fig, ax
# Your code here

Hint

Use import matplotlib.pyplot as plt and plt.subplots() to create the plot area.

3

Plot the lines with different line styles

Use ax.plot() to plot the three lines with x and y1, y2, y3. Set the linestyle parameter to 'solid' for y1, 'dashed' for y2, and 'dotted' for y3. Add labels 'Solid', 'Dashed', and 'Dotted' respectively.

Matplotlib

import matplotlib.pyplot as plt

x = [0, 1, 2, 3, 4]
y1 = [0, 1, 4, 9, 16]
y2 = [0, 1, 2, 3, 4]
y3 = [0, 1, 8, 27, 64]

fig, ax = plt.subplots()

# Plot y1 with solid, y2 with dashed, y3 with dotted line styles
# Your code here

Hint

Use ax.plot() three times with the correct linestyle and label parameters.

4

Add legend and show the plot

Use ax.legend() to add a legend to the plot. Then use plt.show() to display the plot.

Matplotlib

import matplotlib.pyplot as plt

x = [0, 1, 2, 3, 4]
y1 = [0, 1, 4, 9, 16]
y2 = [0, 1, 2, 3, 4]
y3 = [0, 1, 8, 27, 64]

fig, ax = plt.subplots()

ax.plot(x, y1, linestyle='solid', label='Solid')
ax.plot(x, y2, linestyle='dashed', label='Dashed')
ax.plot(x, y3, linestyle='dotted', label='Dotted')

# Add legend and show the plot
# Your code here

Hint

Call ax.legend() before plt.show() to display the legend on the plot.

Practice

1. Which linestyle value in matplotlib creates a solid line?

easy

A. "-"

B. "--"

C. ":"

D. "-."

Solution

1. Step 1: Understand line style symbols in matplotlib

   In matplotlib, the linestyle parameter uses symbols: "-" for solid, "--" for dashed, ":" for dotted, and "-." for dash-dot.

2. Step 2: Match symbol to solid line

   The symbol "-" represents a solid line style.

3. Final Answer:

   "-" -> Option A

4. Quick Check:

   Solid line = "-" [OK]

Hint: Solid line uses a single dash "-" [OK]

Common Mistakes:

• Confusing dashed "--" with solid
• Using ":" for solid line
• Mixing dash-dot "-." with solid

2. Which of the following is the correct syntax to plot a dashed line using matplotlib.pyplot?

easy

A. plt.plot(x, y, linestyle='-')

B. plt.plot(x, y, linestyle=':')

C. plt.plot(x, y, linestyle='--')

D. plt.plot(x, y, linestyle='solid')

Solution

1. Step 1: Recall linestyle values for dashed lines

   Dashed lines in matplotlib are specified by the string "--" or the word "dashed".

2. Step 2: Identify correct syntax

   Among the options, only linestyle='--' correctly sets a dashed line.

3. Final Answer:

   plt.plot(x, y, linestyle='--') -> Option C

4. Quick Check:

   Dashed line = "--" [OK]

Hint: Dashed line uses double dash "--" [OK]

Common Mistakes:

• Using single dash '-' for dashed line
• Using ':' which is dotted line
• Using 'solid' string incorrectly

3. What will be the line style of the plot generated by this code?

import matplotlib.pyplot as plt
x = [1, 2, 3]
y = [2, 3, 5]
plt.plot(x, y, linestyle=':')
plt.show()

medium

A. Dotted line

B. Dashed line

C. Solid line

D. Dash-dot line

Solution

1. Step 1: Identify linestyle parameter value

   The code uses linestyle=':', which in matplotlib means a dotted line.

2. Step 2: Understand line style mapping

   "-" is solid, "--" is dashed, ":" is dotted, and "-." is dash-dot.

3. Final Answer:

   Dotted line -> Option A

4. Quick Check:

   Colon ":" means dotted line [OK]

Hint: Colon ":" means dotted line style [OK]

Common Mistakes:

• Thinking ':' is dashed line
• Confusing dash-dot '-.' with dotted
• Assuming default solid line

4. The following code is intended to plot a dashed line but does not work as expected. What is the error?

import matplotlib.pyplot as plt
x = [0, 1, 2]
y = [0, 1, 4]
plt.plot(x, y, linestyle='dash')
plt.show()

medium

A. The list y has wrong values

B. The linestyle value 'dash' is invalid; use '--' instead

C. Missing plt.show() call

D. The variable names x and y are incorrect

Solution

1. Step 1: Check valid linestyle values in matplotlib

   Matplotlib accepts 'solid', 'dashed', 'dashdot', 'dotted' as strings or symbols like '--', '-.', ':'. The string 'dash' is invalid.

2. Step 2: Identify the error

   The code uses linestyle='dash', which is not a valid linestyle value. Use '--' for dashed lines.

3. Final Answer:

   The linestyle value 'dash' is invalid; use '--' instead -> Option B

4. Quick Check:

   Invalid 'dash'; use '--' [OK]

Hint: 'dash' invalid for dashed; use '--' [OK]

Common Mistakes:

• Assuming 'dash' string works
• Thinking plt.show() is missing
• Blaming variable names or data values

5. You want to plot two lines on the same graph: the first one solid and the second one dotted. Which code correctly sets these line styles?

hard

A. plt.plot(x, y1, linestyle='-.')
plt.plot(x, y2, linestyle=':')

B. plt.plot(x, y1, linestyle=':')
plt.plot(x, y2, linestyle='-')

C. plt.plot(x, y1, linestyle='-')
plt.plot(x, y2, linestyle='--')

D. plt.plot(x, y1, linestyle='-')
plt.plot(x, y2, linestyle=':')

Solution

1. Step 1: Identify line styles for solid and dotted

   Solid line uses "-" and dotted line uses ":" in matplotlib.

2. Step 2: Match code to required styles

   plt.plot(x, y1, linestyle='-') plt.plot(x, y2, linestyle=':') uses linestyle='-' for the first line (solid) and linestyle=':' for the second line (dotted), which is correct.

3. Final Answer:

   plt.plot(x, y1, linestyle='-') and plt.plot(x, y2, linestyle=':') -> Option D

4. Quick Check:

   Solid = '-', Dotted = ':' [OK]

Hint: Solid '-' and dotted ':' line styles together [OK]

Common Mistakes:

• Mixing dashed '--' with dotted ':'
• Using dash-dot '-.' instead of dotted
• Swapping line styles order