Remove lines with an infinite value from array

Question

I have a numpy array

A = np.array([[1, 2, 3, 4], 
             [2, float('inf'), 3, 4],
             [5, 6, 7, 8]])

I would like to remove the lines that contain an infinite value in them so that the results would be

np.array([[1,2,3,4],
          [5,6,7,8]])

I tried to do A = A[float('inf') not in A], but the result is array([], shape=(0, 3, 4), dtype=float64).

I could do

B = []
for line in A:
    if float('inf') not in line:
        B.append(line)
A = np.array(B)

but is there a better way to do this?

yatu · Accepted Answer · 2020-02-03 15:35:15Z

3

Given that you have a NumPy array, a NumPy based solution will perform much better than using python lists.You can use np.isinf with any here:

A[~np.isinf(A).any(1)]

array([[1., 2., 3., 4.],
       [5., 6., 7., 8.]])

is_inf = np.isinf(A) # returns True when there is an Inf
print(is_inf)

array([[False, False, False, False],
       [False,  True, False, False],
       [False, False, False, False]])

is_inf_any = is_inf.any(1) # Checks is there are any Trues along axis 1 
                           # (hence reduces along that axis)
print(is_inf_any)

# array([False,  True, False])

~is_inf_any # applies a bitwise logical not
# array([ True, False,  True])

edited Feb 3, 2020 at 15:35

answered Feb 3, 2020 at 14:53

yatu

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5 Comments

Mihai Alexandru-Ionut Over a year ago

Nice answer. What does it mean any(1) ?

usernumber Over a year ago

What does the ~ mean?

Prashant Kumar Over a year ago

~ means not. That means not isinf

Prashant Kumar Over a year ago

.any(1) means it is checking if any line evaluates to True.

usernumber Over a year ago

And the 1 in .any(1) is the axis along which to perform the comparison, I think

Mihai Alexandru-Ionut · Accepted Answer · 2020-02-03 14:53:30Z

1

You could use a list comprehension for this.

A = np.array([line for line in A if float('inf') not in line])

answered Feb 3, 2020 at 14:53

Mihai Alexandru-Ionut

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