[SciPy-User] [SciPy-user] help about lfilter ????

[persia]

lfilter is the linear filtering function in the scipy.signal module. can
someone tell me what is wrong with this function please ?

I used this function in the following way and it gave me that error !! :

In [204]:
lfilter(array([1,2,3]),array([-4,5,6]),array([9,8,7,6,5,4,3,2,1]),zi=array([0,0]))
---------------------------------------------------------------------------
<type 'exceptions.ValueError'>            Traceback (most recent call last)



<type 'exceptions.ValueError'>: linear_filter not available for this type

 
why is it so ??!!!! what is wrong with this "type " ? what is it meant by
this type anyway ?! i tried with the same arguments in matlab with the
corresponding function and it worked !!
and if i multiply the second argument vector say by .4, this will happen : 

lfilter(array([1,2,3]),.4*array([-4,5,6]),array([9,8,7,6,5,4,3,2,1]),zi=array([0,0]))


(array([   -5.625     ,   -23.28125   ,   -68.7890625 ,  -148.40820312,
        -312.44384766,  -633.16711426, -1276.37466431, -2557.71900177,
       -5120.46074867]),
 array([-10242.1544385 ,  -7682.56612301]))


see ? no problem then ?!! isnt this wierd ? please help !

thanx
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