Open Tableau with superstore data.

    1. Drag order date as a continuous month on the columns shelf and category on the rows.
    2. Just to have an idea about the sales for each category drag sales on the rows.
    3. Now to have two dates into consideration we have two make two parameters 1. Parameter Select Date and b) Parameter Date Comparison which is duplicate of first parameter with different current Date values. Show these parameters by doing right click on them
    4. Show these parameters by doing right click on them.
    5. Now to make this parameter working for the sales its crucial to create calculated field and recalling this parameter date values in that. Hereafter, Calc-SelectedDateSale and other parameter Calc-ComparisonDateSale were created.
    6. Next, drag the first calculated field (Calc-SelectedDateSale ) on the rows.
    7. Now drop the second calculated field (Calc-ComparisonDateSale ) into the first calculated field axis to form a shared axis. As soon the calculated field is close to the axis the ruler-kind of shape (shown in green colour) is formed which indicates the right place for the field to be dropped.
    8. Change he mark type to circle and increase the size of circles to have more clarity about the dates chosen. One may change the colour of the calculated fields from the colour palette appeared on the right-hand side.
    9.  To do a dual axis, right click on Measure values and select dual axis. And then synchronize and remove headers.
    10.  Make another calculated field to find % change as shown in the figure and then place this calculated field on the row shelf
    11.  Bring this calculated field to rows shelf and change the field to discrete value by right clicking the field. The results of % change will appear in one of the columns in the viz
The Data School
Author: The Data School