使用Google表格，如何根据多行计算每月平均值？

Question

I have a spreadsheet where I am entering Groceries on each row every time I visit a store. I have calculated the overall sum, but now I would like to calculate the average cost per month for the groceries.

I don't even know where to begin on this. I have posted my spreadsheet ( https://docs.google.com/spreadsheets/d/1R0zYMAigDULzm8oM2icsPK55BP162kVvctpx2cOSOIE/edit?usp=sharing ).

Answer 1

Try this in B5. It will take the year and month into account (so 1/7/2018 will count as a separate month from 1/7/2017). It counts unique year-month combinations and divides the sum spent. The minus one accounts for the blank cell counted as unique.

=sum(B9:B)/arrayformula(countunique(text(A9:A,"YYYY-MM"))-1)

Answer 2

same answer, using double query:

=QUERY( QUERY({A8:B}, "select year(Col1), month(Col1), sum(Col2) group by year(Col1), month(Col1)"), "select avg(Col3) label avg(Col3) ''")

The inside query is report with sums by years and months:

formula:

=QUERY({A8:B}, "select year(Col1), month(Col1), sum(Col2) group by year(Col1), month(Col1)")

result:

year(Date)  month(Date) sum Amount

2016            10          133.00
2017            0            80.00
2017            1           420.00

Months are zero-based: 0 - Jan, 2 - Feb...