Select all elements from one column in an array of arrays in Ruby?

You want arr.map {|row| row[2]}

arr = [["Foo1", "Bar1", "1", "W"], 
["Foo2", "Bar2", "2", "X"], 
["Foo3", "Bar3", "3", "Y"], 
["Foo4", "Bar4", "4", "Z"]]

arr.map {|row| row[2]}
# => ["1", "2", "3", "4"]