Iteratively Subtract Values In Array

Starting from a simple numpy array like: a = np.array([1,1,0,2,1,0]) my goal is to iteratively subtract values from this till a certain threshold. For instance, think of a includi

Solution 1:

If you want to randomly decrement a.sum() by n without any element of a becoming negative, this is one way to do it:

def rnd_decrement(a, n):
    c = np.cumsum(np.r_[0, a])
    if n < c[-1]:
        r = np.random.choice(np.arange(c[-1]) + 1, n, replace = False)
        d = np.sum(r[:,None] <= c[None,:], axis=0)
        return np.diff(c-d)
    else:
        return np.zeros_like(a)