About alternatives to Matlab

[sturlamolden]

sturlamolden wrote:

> def D4_Transform(x, s1=None, d1=None, d2=None):
>    """
>    D4 Wavelet transform in NumPy
>    (C) Sturla Molden
>    """
>    C1 = 1.7320508075688772
>    C2 = 0.4330127018922193
>    C3 = -0.066987298107780702
>    C4 = 0.51763809020504137
>    C5 = 1.9318516525781364
>    if d1 == None:
>       d1 = numpy.zeros(x.size/2)
>       s1 = numpy.zeros(x.size/2)
>       d2 = numpy.zeros(x.size/2)
>    odd = x[1::2]
>    even = x[:-1:2]
>    d1[:] = odd[:] - C1*even[:]
>    s1[0] = even[0] + C2*d1[0] + C3*d1[-1]       #typ0
>    s1[1:] = even[1:] + C2*d1[1:] + C3*d1[:-1]   #typo
>    d2[0] = d1[0] + s1[-1]
>    d2[1:] = d1[1:] + s1[:-1]
>    even[:] = C4 * s1[:]
>    odd[:] = C5 * d2[:]
>    if x.size > 2:
>    D4_Transform(even,s1[0:even.size/2],
>            d1[0:even.size/2],d2[0:even.size/2])


Actually, there was a typo in the original code. I used d1[l-1] where I
should have used d1[l+1]. Arrgh. Here is the corrected version, the
Matlab code must be changed similarly. It has no relevance for the
performance timings though.




def D4_Transform(x, s1=None, d1=None, d2=None):
    """
    D4 Wavelet transform in NumPy
    (C) Sturla Molden
    """
    C1 = 1.7320508075688772
    C2 = 0.4330127018922193
    C3 = -0.066987298107780702
    C4 = 0.51763809020504137
    C5 = 1.9318516525781364
    if d1 == None:
       d1 = numpy.zeros(x.size/2)
       s1 = numpy.zeros(x.size/2)
       d2 = numpy.zeros(x.size/2)
    odd = x[1::2]
    even = x[:-1:2]
    d1[:] = odd[:] - C1*even[:]
    s1[:-1] = even[:-1] + C2*d1[:-1] + C3*d1[1:]
    s1[-1] = even[-1] + C2*d1[-1] + C3*d1[0]
    d2[0] = d1[0] + s1[-1]
    d2[1:] = d1[1:] + s1[:-1]
    even[:] = C4 * s1[:]
    odd[:] = C5 * d2[:]
    if x.size > 2:
    D4_Transform(even,s1[0:even.size/2],
            d1[0:even.size/2],d2[0:even.size/2])