A step area chart tells you the increase and decrease of sales compared to the previous months. For each month, the step line connects the previous sales with the current.
Step 1: You need a calculated field for the sum of sales of the current month
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_1.png)
Step 2: You need a calculated field for the sum of sales of the previous month
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_2.png)
The lookup function will bring back the value from the previous time period in the view (in this case, month)
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_3.png)
Step 3: Put the two calculated field on Rows, combined axis
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_5.png)
Step 4: Remove Measure Names from the colour shelf, make it a Line graph
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_4.png)
You can also change it to an Area chart
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_6.png)
The advantage of using a step area chart is you can easily highlight the variance of sales over month.
Step 1: Put the sales value of current month on Rows, make it a Gantt Bar
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_7.png)
Step 2: Create a calculated field for Month over Month change
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_8.png)
Step 3: Put the negative value MoM change on the Size shelf, make the bars thinner
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_9.png)
Now if you Dual axis and give the Gantt Bars another colour, you would be able to see the biggest change over month. One good example from a Workout Wednesday is you can colour code the biggest increase and decrease of each category.
Create a calculated field and put it on the colour shelf
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_10.png)
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_11.png)
This is the basic idea of how to build a step area chart and when to use it, you can add some labels and clean up the grid lines to make the chart more appealing.
![](https://www.thedataschool.co.uk/content/images/wordpress/2020/05/Capture1_12-1-1024x507.png)