decision-ex

My first attempt at Elixir, a basic implementation of decision trees. Implementation based on the Decision Trees 2017 Haskell exam for first year Computing students at Imperial College London, course taught by Tony Field. Spec available at: https://www.doc.ic.ac.uk/~ajf/haskelltests/decisiontrees/spec.pdf

How to use

Using the Elixir interpreter:

$ iex utils.exs 
Erlang/OTP 20 [erts-9.1] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] [kernel-poll:false]

Interactive Elixir (1.5.2) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> c "decisionTree.exs"
[DecisionTree]
iex(2)> c "attSelector.exs" 
[AttSelector]
iex(3)> c "naiveAttSelector.exs"
[NaiveAttSelector]
iex(4)> c "informationGainSelector.exs"
[InformationGainSelector]
iex(5)> DecisionTree.buildTree DecisionTree.fishingData, DecisionTree.result, InformationGainSelector
{:node, "outlook",
 [{"sunny", 
   {:node, "humidity",
    [{"high", {:leaf, "bad"}}, {"normal", {:leaf, "good"}}]}},
  {"overcast", {:leaf, "good"}},
  {"rainy",
   {:node, "wind", [{"windy", {:leaf, "bad"}}, {"calm", {:leaf, "good"}}]}}]}
iex(6)> DecisionTree.buildTree DecisionTree.fishingData, DecisionTree.result, NaiveAttSelector       
{:node, "outlook",
 [{"sunny", 
   {:node, "temp",
    [{"hot", {:leaf, "bad"}},
     {"mild",
      {:node, "humidity",
       [{"high", {:leaf, "bad"}}, {"normal", {:leaf, "good"}}]}},
     {"cool", {:leaf, "good"}}]}}, {"overcast", {:leaf, "good"}},
  {"rainy",
   {:node, "temp",
    [{"hot", {:null}},
     {"mild",
      {:node, "humidity",
       [{"high",
         {:node, "wind",
          [{"windy", {:leaf, "bad"}}, {"calm", {:leaf, "good"}}]}},
        {"normal", {:leaf, "good"}}]}},
     {"cool",
      {:node, "humidity",
       [{"high", {:null}},
        {"normal", 
         {:node, "wind",
          [{"windy", {:leaf, "bad"}}, {"calm", {:leaf, "good"}}]}}]}}]}}]}