# [SciPy-user] histogram(a, normed=True) doesn't normalize?

Robert Kern robert.kern at gmail.com
Mon Jun 19 21:46:46 CDT 2006

Martin Spacek wrote:
> David Huard wrote:
>
>>Yes.
>>
>>The normalization constant is not the sum of the bin, but the sum of the
>>product of the bin count with the bin width :
>>\sum_i  f_i * delta_i
>
> It seems I long ago forgot the distinction between a probability
> *distribution* function and a probability *density* function. I assumed
> they were the same thing. Thanks for the clarification.

No, they're the same (more or less). However, what you were asking about (bins
sum to 1) is a probability *mass* function.

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma