python numpy array, sub-array with satisfied condition problem

Question

For example, I have an array X = np.array([1,-3,5,0,9,12])

I wanna make a function a like this.

def bigfunction(X)
    if X<0:
        return 99
    if X=>0 and X<=10
        return 100
    if X>10
        return 101

Which return also an array. In this case [100,99,100,100,100,101] Obviously, this code will not work. It is very import that I can't do it in a loop. I am wondering that if there has implemented the code in numpy solve this problem.

sacuL · Accepted Answer · 2018-09-03 18:30:56Z

2

You can try np.select:

conds = [X < 0, X <= 10]

choices = [99, 100]

np.select(conds, choices, default=101)

This will return:

array([100,  99, 100, 100, 100, 101])

answered Sep 3, 2018 at 18:30

sacuL

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Comments

user2653663 · Accepted Answer · 2018-09-03 18:31:18Z

2

Y = np.zeros(X.shape, dtype=int)
Y[X<0] = 99
Y[(X>= 0) & (X<10)] = 100
Y[X>10] = 101

Where Y will be your returned array.

answered Sep 3, 2018 at 18:31

user2653663

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1 Comment

Mad Physicist Over a year ago

You can also use np.zeros_like(X, dtype=np.int)

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