Line styles (solid, dashed, dotted) in Matplotlib - Step-by-Step Execution

Concept Flow - Line styles (solid, dashed, dotted)

Start Plot Setup

↓

Choose Line Style

↓

Solid

↓

Draw Line with Style

↓

Show Plot Output

The flow shows choosing a line style (solid, dashed, dotted), drawing the line with that style, and displaying the plot.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1,2,3], [1,4,9], linestyle='solid')
plt.plot([1,2,3], [2,5,10], linestyle='dashed')
plt.plot([1,2,3], [3,6,11], linestyle='dotted')
plt.show()

This code draws three lines with different line styles: solid, dashed, and dotted.

Execution Table

Step	Action	Line Data	Line Style	Plot State
1	Plot first line	[1,2,3], [1,4,9]	solid	Line 1 added with solid style
2	Plot second line	[1,2,3], [2,5,10]	dashed	Line 2 added with dashed style
3	Plot third line	[1,2,3], [3,6,11]	dotted	Line 3 added with dotted style
4	Show plot	All lines	solid, dashed, dotted	Plot displayed with 3 styled lines

💡 All lines plotted and plot window shown, execution ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
lines	[]	[Line1: solid]	[Line1: solid, Line2: dashed]	[Line1: solid, Line2: dashed, Line3: dotted]	[3 lines with styles]

Key Moments - 2 Insights

Why does the line style change the appearance of the line?

The 'linestyle' parameter controls how the line is drawn: 'solid' is continuous, 'dashed' shows breaks, and 'dotted' shows dots. See execution_table steps 1-3 where each line is added with a different style.

What happens if you omit the linestyle parameter?

Matplotlib uses the default solid line style. This is why in step 1, specifying 'solid' looks the same as default.

Visual Quiz - 3 Questions

Look at the execution_table, what line style is used in step 2?

A dotted

B solid

C dashed

D dashdot

💡 Hint

Check the 'Line Style' column in execution_table row for step 2.

At which step is the dotted line added to the plot?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Action' and 'Line Style' columns in execution_table.

If you remove the linestyle='dashed' from step 2, what happens to the line style?

A It becomes solid

B It becomes dotted

C It disappears

D It becomes dashdot

💡 Hint

Refer to key_moments about default line style when linestyle is omitted.

Concept Snapshot

matplotlib line styles:
Use 'linestyle' parameter in plt.plot()
Options: 'solid', 'dashed', 'dotted'
Controls line appearance
Default is 'solid'
Example: plt.plot(x, y, linestyle='dashed')

Full Transcript

This visual execution shows how matplotlib draws lines with different styles. First, a solid line is plotted, then a dashed line, and finally a dotted line. Each step adds a line with the specified style to the plot. The variable 'lines' tracks the lines added. The plot is shown with all three lines visible. The linestyle parameter changes how the line looks: solid is continuous, dashed has breaks, dotted shows dots. If linestyle is omitted, the line is solid by default.

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