# How to select the split point for Continuous Attribute Age

For the above table, midpoints for possible split points are 22.5 and 35. I have calculated the entropy and gain for each value and 35 had the minimum Entropy and highest gain. Is it correct ?

Given High -> (-), and Low -> (+)

D<22.5 => [0+, 2-], Entropy (D<22.5) = 0, since all the values are of the same class High.

D>22.5 => [2+, 2-], Entropy (D>22.5) = 1, since the values are distributed equally among Low and High classes.

D<35 => [2+, 3-], Entropy (D<35) = -[2/6 x $$log_2$$(2/6) + 3/6 x $$log_2$$⁡(3/6)]= 0.5

D>35 => [0+, 1-], Entropy (D>35) = 0, since all the values are of the same class High

Gain (D, Age>22.5) = 0.918 - 2/6 (0) - 4/6 (1) = 0.2513

Gain (D, Age>35) = 0.918 - 5/6 (0.5) - 1/6 (0) = 0.5103

Is that right?

D<35 => [2+, 3-], Entropy (D<35) = -[2/5 x $$log_2$$(2/5) + 3/5 x $$log_2$$⁡(3/5)]