Average monthly income in Numbers 3

Question

I use numbers to keep the books and I am trying to get the total for each month automatically. To simplify things, let's assume column A contains the date and B the amount. Out of this, I am trying to return the total for each mont in a separate table. I would expect it to say APR: 200, JUN: 400, JUL 150 and so on.
A                    B  
02 APR          250
05 APR          -50
03 JUN          100
15 JUN          300
08 JUL           150
Any thoughts on how to do this?
Thanks in advance.

Answer 1

Hi Christian,
Here we go. This is not an automatic timestamp, but it goes some way to answer your question:
to fill the A column with the current date when inputing something new into the B column?
Slight alteration, the amounts go into the C column:
This uses =NOW() in column A. The data format is Date & Time to display only the date part.
NOW() is not a timestamp; it insert the current Date & Time and continues to update.
To "freeze" it at an instant in time, select the cell, Copy, then Menu > Edit > Paste Formula Results. More on that later.
B2 contains this formula (and Fill Down):
=IF(LEN(C2)>0,MONTHNAME(MONTH(A2)),"")
If the length (LEN) of a cell in C is greater than 0 (the cell is not empty) then grab MONTH  (a number) from A and convert it to the MONTHNAME
else insert "" (NULL).
B shows the month to fit SG's solution of using SUMIF to add monthly totals.
Save As Template.
In use, make an entry in column C:
The month name appears. Immediately "freeze" the cell in A (Copy, then Menu > Edit > Paste Formula Results) so it will no longer update. To be doubly sure, you may want to "freeze" the month in B at the same time. The rows below the entry are still free to update, waiting for the next entry and "freezing".
Your workflow is: if there is an entry in C, then A and B in that row must be frozen (select, command c, shift command v).
Regards,
Ian.