CODEWITHSUNDEEP
pythonpandaszerodivide-by-zero
mathella
mathella

Reputation: 81

Why do I get infs when I divide by 0 in pandas?

All

I have two columns and I divide one by the other with colb being my denominator. When I divide one by the other however I get infs when there is 0 present in my colb e.g

df[cola]/df[colb]

Mathematically this is correct right? Just wondering if this is expected with pandas . Fir me it makes no sense to have these infs so I will probably replace with 0 but wanted to check

Upvotes: 2

Views: 377

Answers (1)

Serge de Gosson de Varennes
Serge de Gosson de Varennes

Reputation: 11504

For x≠0 , and x∈R , the limits of x/0 as we approach from the left and right hand sides of 0 differ. Hence, it's not defined.

Consider approaching the limit from the right hand side. As the denominator gets smaller and smaller, the value will approach ±∞ depending upon the sign of x . If x>0 , the limit will approach ∞ and if x<0 , the limit approaches −∞ .

If we approach the limit from the left, if x>0 , the limit approaches −∞ and similarly ∞ when x<0 .

In both cases, there is a discontinuity when the denominator approaches 0 and hence x/0 is undefined.

Hence, even in pandas this should yield. However, it is a convention that x/0 is inf if x>0, -inf if x<0

Upvotes: 2

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