At my first ever geography teacher institute, at Macalester College in 1986, one of the leaders held up a data table and said "Look at this table! Just look at it! You can just … just … put your ear up close, like this, y'see … and hear it crying out … 'I wanna be a map!'" Ever since the dawn of ArcView2 -- long before "mashups" became popular -- I've been happily joining external data tables to shapefiles in order to make dozens of new maps.

I never tire of it. To this day, joining tables to existing features remains, in my mind, one of the most powerful capacities of GIS. It opens up vast galaxies of exploration! And talk about math! Going through banks of numbers and looking at ways to classify them, query them, normalize one by another, sort and sum and statisticalize them (huh?), is a powerful way to build understanding of a given data set, and how one item relates to another.

The other day, I saw an email from the National Center from Education Statistics, describing new data about public schools from the 2007-08 school year. The PDF document had a set of six tables about the 50 states. I downloaded it and took about 20 minutes to convert them into one long spreadsheet (Excel file). Then it was time to play with the data.

Above you can see one look at the student/teacher ratio. Below, you can see one look at the ratio of students eligible for free or reduced lunch. (It also helps to look at the original PDF document.)

There's never an end of data to explore. Joining data tables to existing features is a piece of cake in ArcView. Try it, and maybe you too will be able to look at the table and hear it crying out … just listen … it wants to be a map!

- Charlie Fitzpatrick, Co-Manager, ESRI Schools Program