[Numpy-discussion] numpy.random.multinomial() cannot handle zero's

Michael Nandris mnandris at btinternet.com
Sun Aug 26 08:45:55 EDT 2007

Is there an easy way around this problem, that does not involve fixing the API (like using NaN instead of 0.0)?

>>> from numpy.random import multinomial 
>>> multinomial(100,[ 0.2, 0.4, 0.1, 0.3 ])
array([19, 45, 10, 26])
>>> multinomial( 100, [0.2, 0.0, 0.8, 0.0] )
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "mtrand.pyx", line 1173, in mtrand.RandomState.multinomial
TypeError: exceptions must be strings, classes, or instances, not exceptions.ValueError

I found a similar problem in scipy.stats.rv_discrete() which was fixed by adding sort to a dictionary handler: 

def reverse_dict(dict):
    newdict = {}
    for key in dict.keys():            #  DUFF
        newdict[dict[key]] = key
    return newdict

def reverse_dict(dict): 
    newdict = {} 
    for key in dict.keys(): 
        sorted_keys = copy(dict.keys()) 
    for key in sorted_keys[::-1]:         # NEW
        newdict[dict[key]] = key 
    return newdict 

Obviously this cannot be done with numpy since it runs in C or something which I don't understand. Can anyone help? Numpy is great and the simulation I want to code requires speed.

Thanks for any advice given

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