I've set a Trendline for a Chart Series to Moving Average, but the Period only accepts a maximum of 10 periods.
The data is provided as Weekly Stock Prices, using GOOGLEFINANCE(), for the last 10 years.
I would like to see a trendline over a longer period, such as 26 (weeks). Ideally, I would specify this Period in a sheet cell, so I can change it depending on the stock I'm interested in.
One option I thought might work is to add an extra column that works out an average, and use that as another Series? However I don't know how to specify the number of Periods in such a calculated Average().
Is there any method to do this?