Waterfall chart pattern in Matplotlib - Step-by-Step Execution

Concept Flow - Waterfall chart pattern

Start with initial value

↓

Add positive changes

↓

Subtract negative changes

↓

Calculate intermediate totals

↓

Plot bars step-by-step

↓

Show final total bar

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End

A waterfall chart starts with an initial value, then adds or subtracts changes step-by-step, showing intermediate totals and a final total bar.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
values = [100, -20, 30, -10, 40]
labels = ['Start', 'Loss', 'Gain', 'Loss', 'Gain']
plt.bar(range(len(values)), values)
plt.show()

This code plots simple bars for each value, but does not yet show the waterfall pattern with cumulative totals.

Execution Table

Step	Index	Value	Running Total	Bar Start	Bar Height	Bar Color
1	0	100	100	0	100	blue
2	1	-20	80	80	20	red
3	2	30	110	80	30	blue
4	3	-10	100	110	10	red
5	4	40	140	100	40	blue
6	Total		140	0	140	green

💡 All values processed, final total bar shows cumulative sum 140

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
running_total	0	100	80	110	100	140	140
bar_start	0	0	80	80	110	100	0
bar_height		100	20	30	10	40	140
bar_color		blue	red	blue	red	blue	green

Key Moments - 3 Insights

Why does the bar start position change for negative values?

Negative values are drawn downward from the current running total, so the bar start is the running total before this step (see execution_table rows 2 and 4).

How is the final total bar different from other bars?

The final total bar starts at zero and its height is the cumulative sum of all values, shown in execution_table row 6 with color green.

Why do some bars have red color and others blue?

Positive values use blue bars to show increases, negative values use red bars to show decreases, as tracked in variable_tracker 'bar_color'.

Visual Quiz - 3 Questions

Look at the execution table, what is the running total after step 3?

A 80

B 110

C 100

D 140

💡 Hint

Check the 'Running Total' column at step 3 in the execution_table.

At which step does the bar color change to red for the first time?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Bar Color' column in execution_table rows.

If the value at index 1 changed from -20 to -50, what would be the new running total after step 2?

A 50

B 80

C 30

D 100

💡 Hint

Subtract 50 from the initial 100 to find the new running total after step 2.

Concept Snapshot

Waterfall chart pattern:
- Start with initial value
- Add/subtract changes stepwise
- Bars start at previous total
- Positive bars in one color, negative in another
- Final bar shows total sum

Full Transcript

A waterfall chart visually shows how an initial value changes step-by-step by adding or subtracting amounts. Each bar starts where the previous bar ended, with positive changes going up and negative changes going down. The final bar shows the total after all changes. This pattern helps understand how individual parts affect the whole.