Moving Average Trendline - Period Usage?

KariMiller  wrote:  ``I'm trying to add a trendline that will show the moving month over month average for this time period. However, I do not understand what I should enter in the "Period" field. [....] I hope I provided enough information``

Not really.

First, "period" just refers to the number of "data points" to average.

If you think of the moving average as a window on the data that moves left to right, "period" is the width of the window.

I think you want a "monthly" moving average.  But we really cannot say how many data points comprise a "month", since that varies from month to month.

If you have stock data, and the data points are just trade days, there are typically 252 trade days in a year and 21 trade days in a month.

If your data is not trade days, it might help us to know how you pared down 7471 days between 1/1/2003 and 6/15/2023 to 5157.  IOW, what is your data comprised of?

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Second, that will not align with "month over month" data points.  But I don't think anything can, unless you vary the moving average "window" based on actual dates.

If you want to do that, you cannot use the chart trendline for that purpose.

Instead, I would do the moving average calculation in a parallel column.

And I would use a VBA procedure in order to handle the case where you don't have date for "one month later".

It is really quite messy.  For that reason, I would not recommend it.