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Posted By

adkatrit on 02/11/11


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entropy


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adkatrit


Entropy

 / Published in: Python
 

takes a list and returns the entropy

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  1. def entropy(l):
  2. 	from math import log
  3. 	log2=lambda x:log(x)/log(2)
  4.  
  5. 	total=len(l)
  6. 	counts={}
  7. 	for item in l:
  8. 		counts.setdefault(item,0)
  9. 		counts[item]+=1
  10.  
  11. 	ent=0
  12. 	for i in counts:
  13. 		p=float(counts[i])/total
  14. 		ent-=p*log2(p)
  15. 	return ent

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