algorithm - How to calculate decision tree and Entropy? -

given values such x1,x2,x3 as

x1  x2  x3  y  0   0   0   1  2   3   4   0  -1  5   9   0  6   3  -1   1  3   3   3   0  

i need mathematical solution like

s=iplog2p-(1-p)log2(1-p) (formul solution)