I have a series of weekly data points over a 20 year period and i want
to calculate the average for each month during that period in excel.
Are the data raw numbers (e.g. stock prices), or are the data
percentages (e.g. weekly percentage change)?
If the latter, are you interested in the average weekly percentage
change each month, or are you interested in the compounded monthly
growth rate?
If you would like help with that decision, it would be helpful if you
described your application. How do you intend to use the monthly
data? For example, Monte Carlo simulation? Informal accounting
reports? Formal accounting reports, which must follow certain
regulation and GAAP?
Lastly, you mentioned that you have "weekly data points". Does that
include dates? If not, how are the weekly data organized? That is,
how can we distinguish one month's weekly data from another month's?
These are all questions that you might want to think about, even if
someone provides what appears to be a turn-key solution for you.
