python實現matlab中的filter函數

matlab中的filter函數：

y = filter(b,a,x)

python實現matlab中的filter函數

def filter_matlab(b,a,x): y = [] y.append(b[0] * x[0]) for i in range(1,len(x)): y.append(0) for j in range(len(b)): if i >= j : y[i] = y[i] + b[j] * x[i - j ] j += 1
        for l in range(len(b)-1 ): if i >l: y[i] = (y[i] - a[l+1] * y[i -l-1]) l += 1 i += 1
    return y

example:

取

b =  [8,-3.5,0.5]

a =  [1,-1.5,0.25]

x = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]

y = filter_matlab(b,a,x)

函數的結果和matlab的filter函數結果一致，為

[8,
 24.5,
 52.25,
 94.75,
 156.5625,
 243.65625,
 363.84375,
 527.3515625,
 747.56640625,
 1042.01171875,
 1433.6259765625,
 1952.43603515625,
 2637.74755859375,
 3541.0123291015625,
 4729.581604003906,
 6291.619323730469,
 8342.533584594727,
 11033.395545959473,
 14561.959922790527,
 19187.090997695923]