import numpy as np
import math

class IG():
  def __init__(self,X,y):

    X = np.array(X)
    n_feature = np.shape(X)[1]
    n_y = len(y)

    orig_H = 0
    for i in set(y):
      orig_H += -(y.count(i)/n_y)*math.log(y.count(i)/n_y)

    condi_H_list = []
    for i in range(n_feature):
      feature = X[:,i]
      sourted_feature = sorted(feature)
      threshold = [(sourted_feature[inde-1]+sourted_feature[inde])/2 for inde in range(len(feature)) if inde != 0 ]

      thre_set = set(threshold)
      if float(max(feature)) in thre_set:
        thre_set.remove(float(max(feature)))
      if min(feature) in thre_set:
        thre_set.remove(min(feature))
      pre_H = 0
      for thre in thre_set:
        lower = [y[s] for s in range(len(feature)) if feature[s] < thre]
        highter = [y[s] for s in range(len(feature)) if feature[s] > thre]
        H_l = 0
        for l in set(lower):
          H_l += -(lower.count(l) / len(lower))*math.log(lower.count(l) / len(lower))
        H_h = 0
        for h in set(highter):
          H_h += -(highter.count(h) / len(highter))*math.log(highter.count(h) / len(highter))
        temp_condi_H = len(lower)/n_y *H_l+ len(highter)/n_y * H_h
        condi_H = orig_H - temp_condi_H
        pre_H = max(pre_H,condi_H)
      condi_H_list.append(pre_H)

    self.IG = condi_H_list


  def getIG(self):
    return self.IG

if __name__ == "__main__":


  X = [[1, 0, 0, 1],
     [0, 1, 1, 1],
     [0, 0, 1, 0]]
  y = [0, 0, 1]


  print(IG(X,y).getIG())