Thank you for sharing the excel spreadsheet with the detailed information.
Tableau can be used to build the views but you will need some understanding of Table Calculations so I suggest checking out the online learning and various resources for this feature.
In the attached workbook, I have created a data view which shows the layout of the datat (note that I have taken the example excel sheet and defined hard values from your random ones so that things would not change and we could compare the results to the original data. My data is different than your original data examples though. The excel sheet is embedded in the attached .twbx file for your review.
The Data view also contains the field "Difference is values which was originally created by using the drop down menu of Sum(Rating) and selecting Quick Table Calculation - Difference. I then modify the calculation with the edit Table Calculation feature to utilize the specific Dimension of Month of Date while keeping Customer and Industry as unselected. As long as these fields are included in the following views and no additional Dimensions are added, we should retain the values.
Next - copy the viz and move the Customer and Month(Date) fields to the marks shelf. Modify the Diffference is values field to be Discrete (because we want to see the number of these) and place it on the Columsn shelf. Finally place Sum(Number of Records) on the Rows shelf. Add the desired filters and if you like - the Customer to the Colors shelf and you have the desired view.
Note that the filters for month should be used by selecting the two adjacent months that you want to know the difference between or by selecting all of the months to see the count of all of them. Industry is added in the final view as a filter as well for this example.
Others may have some ideas about how to achieve the same outcome as Tableau almost always provides different solutions but this seems like the quickest/easiest one for me. Table calculations do to take some time to understand though so review the attached workbook and then go visit the lessons on this topic (and other resources around the internet) to get going. In no time, you will be a Tableau pro.
Oh - note that you did not mention the version of Tableau in use so I utilized the latest/greatest - Tableau 10.2. If you do not currently run this version, please download and install to open this workbook. You can have different versions of Tableau installed at the same time but the most recently installed version will act as the default one for opening .twb and .twbx files when you double click on one in File Explorer.
Best of luck.
I hope this helps,
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customer migration.twbx 64.2 KB
Thank you so much for your help and the detailed explanation! I was struggling to turn the "calculated difference" to a "dimension" for plotting the chart.