yogi_Compute For DashBoard Number Of Unique Persons Who Visited Designated Cities In Specified Year

                                           Google Spreadsheet   Post  #1954
              Yogi Anand, D.Eng, P.E.      ANAND Enterprises LLC -- Rochester Hills MI     www.energyefficientbuild.com.    May 11, 2015

post by angelbojangles:

https://productforums.google.com/forum/#!category-topic/docs/spreadsheets/qqQl1bvOMiA
How to COUNTIF items in one column only once if there are duplicates in another column?

Sample dummy sheet here

Basically, my goal is to create an interactive graph that works off of countifs from Sheet1. You can see in Sheet1 there are six people (Abby, Bobby, Cindy, Danny, Eddy, and Frankie) who have visited Paris, New York, and London a number of times between 2007-2008.

I'm trying to figure out a countif formula for the interactive graph that counts how many INDIVIDUAL people have visited these cities (in 2007, 2008, or both). So even if Abby visited Paris in 2007 three times, she only gets counted once because she's only one person. 

Does that make sense? 

Thank you!

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