Recurrence with numpy

Question

Is there any way to make recurrence without using for\'s in numpy?

Using np.add with out keyword do the trick with dtype=\"int\"

Answer 1

Since linear recurrences have analytic solutions (here for Fibonacci), an other rapid scipy method is :

def fib_scipy2(N):
    r5=math.sqrt(5)
    phi=(1+r5)/2
    a= (-phi*ones(N)).cumprod()
    return (np.abs(a)-1/a)/r5

Runs :

In [413]: fib_scipy2(8)
Out[413]: array([  1.,   1.,   2.,   3.,   5.,   8.,  13.,  21.])
In [414]: %timeit fib(10**4)
103 µs ± 888 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)

You can tune it to any linear equation.