Sales is aggregated at a daily level. For one chart, I want to display the average monthly sales for each year, meaning the sum of sales for each month divided by 12. Additionally, I would like it to into include years which are not completed. For example, in 2018 it would not include December so it would be the sum of sales for the months already finished divided by 11. In the other chart, I want to display for each month, the average sales for that month across years. For example (Jan2016+Jan2017+Jan2018)/3. And same thing, the December measure would exclude 2018. What would be the formula I would use to for the measure in these charts?
