Difference and percent difference in Tableau - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the difference between sales of the current and previous month.

Tableau

SUM([Sales]) - LOOKUP(SUM([Sales]), [1])

Drag options to blanks, or click blank then click option'

A-1

B0

C1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of -1 as offset.

Using 0 which returns the current row value.

Confusing the direction of offset.

The LOOKUP function with offset -1 gets the previous month's sales, so subtracting it from current sales gives the difference.

2fill in blank

medium

Complete the code to calculate the percent difference between sales of the current and previous month.

Tableau

(SUM([Sales]) - LOOKUP(SUM([Sales]), [1])) / ABS(LOOKUP(SUM([Sales]), [1]))

Drag options to blanks, or click blank then click option'

A1

B0

C-1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of -1 as offset.

Dividing by current sales instead of previous sales.

Not using ABS which avoids division by negative.

The offset -1 in LOOKUP gets the previous month's sales for comparison in percent difference calculation.

3fill in blank

hard

Fix the error in the calculation to correctly compute percent difference in sales.

Tableau

(SUM([Sales]) - LOOKUP(SUM([Sales]), [1])) / LOOKUP(SUM([Sales]), [1])

Drag options to blanks, or click blank then click option'

A0

B1

CABS

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive offset which looks forward.

Using 0 which looks at current row.

Using ABS as offset which is invalid.

The offset -1 is needed to refer to the previous month in the LOOKUP function for correct percent difference.

4fill in blank

hard

Fill both blanks to calculate the difference and percent difference between current and previous sales.

Tableau

Difference: SUM([Sales]) - LOOKUP(SUM([Sales]), [1])
Percent Difference: (SUM([Sales]) - LOOKUP(SUM([Sales]), [2])) / ABS(LOOKUP(SUM([Sales]), [2]))

Drag options to blanks, or click blank then click option'

A-1

B1

C0

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using different offsets for difference and percent difference.

Using positive offsets which look forward.

Using 0 which refers to current row.

Both calculations require offset -1 to refer to previous month sales.

5fill in blank

hard

Fill all three blanks to create a calculated field that returns percent difference formatted as a percentage string.

Tableau

ROUND(((SUM([Sales]) - LOOKUP(SUM([Sales]), [1])) / ABS(LOOKUP(SUM([Sales]), [2]))) * 100, [3]) + "%"

Drag options to blanks, or click blank then click option'

A-1

B0

C2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or positive offsets which refer to current or next rows.

Not rounding or rounding to wrong decimal places.

Forgetting to multiply by 100 to get percentage.

The offsets -1 get previous month sales; rounding to 1 decimal place formats the percent difference nicely.

Practice

1. What does the Difference calculation in Tableau typically show?

easy

A. The total sum of all values

B. The average value over time

C. How much a value changed between two points

D. The maximum value in a dataset

Solution

1. Step 1: Understand the meaning of Difference

   Difference measures the change in value from one point to another, showing increase or decrease.

2. Step 2: Compare with other options

   Sum, average, and maximum describe different calculations unrelated to change between points.

3. Final Answer:

   How much a value changed between two points -> Option C

4. Quick Check:

   Difference = Change amount [OK]

Hint: Difference = New value minus old value [OK]

Common Mistakes:

• Confusing difference with total sum
• Thinking difference shows average
• Mixing difference with maximum value

2. Which of the following Tableau calculations correctly computes the percent difference between the current and previous value?

easy

A. ([Current Value] - [Previous Value]) / [Previous Value]

B. ([Previous Value] - [Current Value]) / [Current Value]

C. [Current Value] + [Previous Value] / [Previous Value]

D. [Current Value] * [Previous Value]

Solution

1. Step 1: Recall percent difference formula

   Percent difference = (New - Old) / Old, showing change relative to original.

2. Step 2: Match formula to options

   ([Current Value] - [Previous Value]) / [Previous Value] matches formula exactly; others either reverse or misuse operations.

3. Final Answer:

   ([Current Value] - [Previous Value]) / [Previous Value] -> Option A

4. Quick Check:

   Percent difference = (New - Old) / Old [OK]

Hint: Percent difference = difference divided by previous value [OK]

Common Mistakes:

• Swapping numerator terms
• Dividing by current value instead of previous
• Using addition or multiplication instead of division

3. Given this Tableau calculated field:
LOOKUP(SUM([Sales]), 0) - LOOKUP(SUM([Sales]), -1)
What does this calculation return?

medium

A. The percent difference in sales between current and previous row

B. The total sales for all rows

C. The sum of sales for the previous row only

D. The difference in sales between the current and previous row

Solution

1. Step 1: Understand LOOKUP function usage

   LOOKUP(SUM([Sales]), 0) returns current row sales; LOOKUP(SUM([Sales]), -1) returns previous row sales.

2. Step 2: Calculate difference

   Subtracting previous from current gives the difference in sales between rows.

3. Final Answer:

   The difference in sales between the current and previous row -> Option D

4. Quick Check:

   LOOKUP difference = sales change [OK]

Hint: LOOKUP with offset -1 gets previous row value [OK]

Common Mistakes:

• Thinking it calculates percent difference
• Assuming it sums all sales
• Confusing current and previous row values

4. You wrote this Tableau formula to calculate percent difference:
(SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / SUM([Sales])
But the results seem incorrect. What is the likely error?

medium

A. Not using WINDOW_SUM instead of SUM

B. Dividing by current sales instead of previous sales

C. Subtracting current sales from previous sales

D. Using LOOKUP with offset -1 incorrectly

Solution

1. Step 1: Analyze denominator in formula

   The formula divides by SUM([Sales]) which is current sales, but percent difference should divide by previous sales.

2. Step 2: Identify correct denominator

   Correct formula divides by LOOKUP(SUM([Sales]), -1) to get previous sales as denominator.

3. Final Answer:

   Dividing by current sales instead of previous sales -> Option B

4. Quick Check:

   Percent difference denominator = previous value [OK]

Hint: Divide by previous value, not current, for percent difference [OK]

Common Mistakes:

• Using current value as denominator
• Confusing subtraction order
• Misusing LOOKUP offset

5. You want to create a Tableau dashboard showing monthly sales percent difference compared to the previous month. Which approach correctly calculates this and handles months with zero sales without errors?

hard

A. Use (SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / NULLIF(LOOKUP(SUM([Sales]), -1), 0) to avoid division by zero

B. Use (SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / SUM([Sales]) ignoring zero sales

C. Use SUM([Sales]) / LOOKUP(SUM([Sales]), -1) without subtraction

D. Use WINDOW_SUM(SUM([Sales])) - WINDOW_SUM(SUM([Sales])) for difference

Solution

1. Step 1: Calculate percent difference with zero check

   Percent difference = (Current - Previous) / Previous; use NULLIF to avoid division by zero errors when previous sales are zero.

2. Step 2: Evaluate options for correctness

   Use (SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / NULLIF(LOOKUP(SUM([Sales]), -1), 0) to avoid division by zero uses NULLIF to prevent errors; others either divide by current or ignore zero sales causing errors or wrong results.

3. Final Answer:

   Use (SUM([Sales]) - LOOKUP(SUM([Sales]), -1)) / NULLIF(LOOKUP(SUM([Sales]), -1), 0) to avoid division by zero -> Option A

4. Quick Check:

   Use NULLIF to handle zero denominator [OK]

Hint: Use NULLIF to prevent division by zero in percent difference [OK]

Common Mistakes:

• Dividing by current sales instead of previous
• Ignoring zero sales causing errors
• Using sum differences without percent calculation