Rolling period calculations in Tableau - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ dax_lod_result

intermediate

Calculate 3-month rolling sum using Tableau LOD expressions

You have monthly sales data. Which Tableau LOD expression correctly calculates the 3-month rolling sum of sales ending at the current month?

A RUNNING_SUM(SUM([Sales]))

B { FIXED [Month] : SUM([Sales]) }

C { INCLUDE [Month] : SUM([Sales]) }

D WINDOW_SUM(SUM([Sales]), -2, 0)

💡 Hint

Think about how to sum sales over the current and previous two months in a rolling window.

WINDOW_SUM with offsets -2 to 0 sums sales for the current month and two prior months, creating a 3-month rolling sum.

❓ visualization

intermediate

Identify the correct rolling average line chart

You want to visualize a 6-month rolling average of revenue over time. Which chart best represents this rolling average?

A Bar chart showing monthly revenue with a 6-month rolling average line overlay

B Line chart with monthly revenue points connected directly

C Pie chart showing revenue distribution by month

D Scatter plot of monthly revenue vs. month number

💡 Hint

Rolling averages are best shown as a smooth line over time to show trends.

A bar chart with monthly revenue and a rolling average line overlay clearly shows both raw data and smoothed trend.

🧠 Conceptual

advanced

Understanding difference between RUNNING_SUM and WINDOW_SUM

Which statement correctly explains the difference between RUNNING_SUM and WINDOW_SUM in Tableau when calculating rolling totals?

A RUNNING_SUM calculates cumulative total from the start to current row; WINDOW_SUM sums over a specified window of rows.

B RUNNING_SUM sums only the current row; WINDOW_SUM sums all rows in the data source.

C RUNNING_SUM and WINDOW_SUM are identical and interchangeable.

D RUNNING_SUM sums over a fixed window; WINDOW_SUM sums cumulatively from the start.

💡 Hint

Think about cumulative totals versus sums over a sliding window.

RUNNING_SUM accumulates values from the first row up to the current row, while WINDOW_SUM sums values within a defined window around the current row.

🔧 Formula Fix

advanced

Identify the error in this rolling average calculation

Given this Tableau calculation for a 12-month rolling average: WINDOW_AVG(SUM([Sales]), 0, 11), what is the problem?

Tableau

WINDOW_AVG(SUM([Sales]), 0, 11)

A SUM([Sales]) cannot be used inside WINDOW_AVG.

B WINDOW_AVG requires three arguments, but only two are provided.

C The window offsets should be negative to include previous months, e.g., -11 to 0.

D The calculation will work correctly as is.

💡 Hint

Rolling averages usually include previous periods, not future ones.

The window offsets 0 to 11 sum the current and next 11 rows, which is forward-looking. For a rolling average including past 12 months, offsets should be -11 to 0.

🎯 Scenario

expert

Design a rolling 4-quarter growth rate calculation

You have quarterly sales data and want to calculate the rolling 4-quarter growth rate in Tableau. Which approach correctly calculates this?

A Use (SUM([Sales]) - LOOKUP(SUM([Sales]), -4)) / LOOKUP(SUM([Sales]), -4)

B Use WINDOW_SUM(SUM([Sales]), -3, 0) / WINDOW_SUM(SUM([Sales]), -7, -4)

C Use RUNNING_SUM(SUM([Sales])) / 4

D Use (SUM([Sales]) - LOOKUP(SUM([Sales]), 4)) / LOOKUP(SUM([Sales]), 4)

💡 Hint

Growth rate compares current 4 quarters sum to previous 4 quarters sum.

Option B calculates sum of current 4 quarters (offsets -3 to 0) and previous 4 quarters (offsets -7 to -4), then divides to get growth rate.