Impact in Power BI of States Reporting Only Once a Week

I’ve noticed that states have stopped reporting coronavirus status every single day, including the weekends, especially in the South. I get it…we’re getting tired of keeping track of how we’re doing (or how we’re not faring). Florida, though, is a state that is on another level so that now my graphs are starting to be deceiving.

Image 1: Daily Cases: For South and Florida in particular

In Image 1, there are three pieces to the image: 1) the left hand side showing line graphs of daily cases for all states in the South; 2) the upper right showing daily cases just for Florida; and 3) lower right table showing the daily cases numbers for Florida for the last few days. On the left hand side, the line for Florida is the bright green one showing the state’s daily cases to be rising way above the other states, but that didn’t seem right. I tried to pull it out singly, which is in the upper right, to see if the graph changes but no, the line slopes upward very steeply. That is not right because I knew that the state was reporting once every 7 days and that is confirmed in the table in the lower right. Look at the dates: the daily reporting ended on 6/4/2021 and started to be once every 7 days.

These graphics were made in Power BI and the source of data came from Wikipedia. Data sources can be found at the end of this post.

So, I tried to see what Excel would do.

Image 2 uses the same Wikipedia data for Florida as in Image 1 but added CDC data for comparison. The CDC data shows Florida’s data for everyday rather than once a week. The blue line is Wikipedia’s data and is what the graphs in Image 1(Power BI) should be showing – the line dropping to zero for 6 days out of 7. Image 3 on the right hand side shows moving averages for both Wikipedia data (blue line) and CDC data (orange line). The Wiki line now falls to what I would expect it to be.

Finally, I went back to Power BI and tried graphing the moving averages.

In Image 4, which comes from Power BI, the left hand side shows the original daily cases for the South and the upper right hand side shows the moving averages for the South. You can see that the moving averages for the other states smooth out the daily jags but for Florida, no changes. If you look at the table in the bottom right corner, you will see that the moving averages for the last few days do not really compute the moving averages as one would expect (I would normally expect to include the zero days to be included in the calculation).

So something is going on with the Power BI. This instance is why it is good to double check the results in Power BI because it can give you unexpected results and maybe not what you want. And it also confirms why I want the data to come in daily, not once a week.