numpy: frequencies

[robert]

I have an integer array with values limited to range(a,b) like:

ia=array([1,2,3,3,3,4,...2,0,1])

and want to speedly count the frequencies of the integers into get a density matrix.
Is this possible without looping?


Question 2: is it possible to compute a "moving maximum" without python looping

ia=array([4,2,1,5,3,2,2,0,1,1]) 
-> mvmax(ia,3) ->
         [4,4,4,5,5,5,3,2,2,1]) 


Robert