Formula (array?) to compute weighted average balance

[BeenHappier]

I have data in 2 columns 1) Date and 2) the Interest Rate for the period
ending on the Date. The dates are irregular and cover many years. I need to
study multiple data sets and there are over 1500 rows in each set.

Given a 3rd column of dates (e.g., 1/1, 2/1, 3/1, etc.), I was hoping to
calculate the weighted average balance for each monthly period ending 1/1/,
2/1, 3/1, etc.

Can I do this with a single array formula?

Only way I have been able to do this is with about 5 columns and SUMIF's
which I think are slowing my computational speeds.

(I've fooled around with PivotTables, but I can't them to work reliably, I
think because I need to update with real time data frequently).

I've never posted before, but given what I've read, I'm optimistic!

Thanks in advance.

 

[Shane Devenshire]

Hi,

Why don't you show us a sample of the data (all three columns) and maybe
what the answer you want for the same it.

Cheers,
Shane Devenshire