yogi_From A Table Of Dates And Amounts Compute Average Amount For Each Month Row By Row And Then Average Amount Per Month

                                          Google Spreadsheet   Post  #1153
Yogi Anand, D.Eng, P.E.      ANAND Enterprises LLC -- Rochester Hills MI     www.energyefficientbuild.com.    Apr 24, 2013
user T Sull :(http://productforums.google.com/forum/?zx=crpyw0e3sdva#!category-topic/docs/spreadsheets/zOjwEJgCj2Y)
Averging Spending Per Month
Hello,
  I have a list of purchases, and I would like to average the amount I have spent per month.

For example

Date:          Cost
1/01/2013    $10
1/15/2013    $15
2/24/2013    $14
2/24/2013    $18
2/28/2013    $21
3/05/2013    $13
3/14/2013    $16

I have been searching and can't seem to find/figure out an easy solution. I am somewhat unfamiliar with all of the native functions too.

Basically I want the formula to extrapolate the average cost for each month from two columns of purchase dates and then average out those averages to give me an actual average spent per month.

Any ideas? I know I can make a hidden table, but was wondering if there was a formula with nested formulas that could accomplish this.

Thanks :)
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following is a solution to the problem