Basic scatter plot with plt.scatter in Matplotlib - Step-by-Step Execution

Concept Flow - Basic scatter plot with plt.scatter

Prepare data points

↓

Call plt.scatter(x, y)

↓

Plot points on graph

↓

Show or save plot

First, we prepare the x and y data points. Then we call plt.scatter to plot these points. Finally, we display the scatter plot.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [10, 20, 25, 30]
plt.scatter(x, y)
plt.show()

This code plots four points on a scatter plot and shows the graph.

Execution Table

Step	Action	Input/Parameters	Result/Output
1	Prepare x data	[1, 2, 3, 4]	x list created
2	Prepare y data	[10, 20, 25, 30]	y list created
3	Call plt.scatter	x=[1, 2, 3, 4], y=[10, 20, 25, 30]	Scatter plot points placed on graph
4	Call plt.show	None	Graph window opens showing scatter plot

💡 Plot displayed and program waits for user to close graph window

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
x	undefined	[1, 2, 3, 4]	[1, 2, 3, 4]	[1, 2, 3, 4]
y	undefined	undefined	[10, 20, 25, 30]	[10, 20, 25, 30]

Key Moments - 2 Insights

Why do we need both x and y lists for plt.scatter?

Because plt.scatter plots points by pairing each x value with a y value, as shown in execution_table step 3.

What happens if plt.show() is not called?

The plot will not appear on screen because plt.show() triggers the display, as seen in execution_table step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of y after Step 2?

A undefined

B [10, 20, 25, 30]

C [1, 2, 3, 4]

D None

💡 Hint

Check the variable_tracker table under 'y' after Step 2 column

At which step does the scatter plot points get placed on the graph?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Result/Output' column in execution_table for Step 3

If we skip plt.show(), what will happen according to the execution flow?

A Plot will still display automatically

B Plot window will open but be empty

C Plot will not display on screen

D Code will error out

💡 Hint

Refer to key_moments explanation about plt.show() and execution_table Step 4

Concept Snapshot

plt.scatter(x, y) plots points with x and y coordinates.
Both x and y must be lists or arrays of same length.
Call plt.show() to display the plot window.
Useful for visualizing relationships between two variables.

Full Transcript

This visual execution shows how to create a basic scatter plot using matplotlib's plt.scatter function. First, we prepare two lists: x and y, which hold the horizontal and vertical coordinates of points. Then, plt.scatter is called with these lists to place points on the graph. Finally, plt.show() displays the plot window so we can see the scatter plot. Variables x and y remain unchanged after creation. Key points include needing both x and y lists and calling plt.show() to see the plot. The execution table traces each step from data preparation to plot display. The quiz tests understanding of variable values and function effects.