2013-02-22-Gini

• Calculate Gini Index

Gini(D) = 1 - sum(frac**2 for frac in classes)

Sum of the squares of the fraction of items in each class

• Calculating the Gini Index for the Candidate Names for the enitre data set
• Partition by zip code, calculate the weighted average Gini Index score over all partitions
• Partitions are weighted by the number of records they contain divided by the total number of records in the data set

• Find a best split of a continuous field

• collections
• defaultdict autovivifies keys
• Counter autovivifies integer keys

zipcodes = defaultdict(Counter)

$ git checkout master
$ git pull jblomo master
$ git checkout -b hw-gini