I have a numpy array that is one dimensional. I would like to get the biggest and the smallest index for which a property is true.
For instance,
A = np.array([0, 3, 2, 4, 3, 6, 1, 0])
and I would like to know the smallest index for which the value of A is larger or equal to 4.
I can do
i = 0
while A[i] < 4:
i += 1
print("smallest index", i)
i = -1
while A[i] <4:
i -= 1
print("largest index", len(A)+i)
Is there a better way of doing this?
As suggested in this answer,
np.argmax(A>=4)
returns 3, which is indeed the smallest index. But this doesn't give me the largest index.
You can try something like. As per the comments, if A is.
A = np.array([0, 3, 2, 4, 3, 6, 1, 4])
idx_values = np.where(A >= 4)[0]
min_idx, max_idx = idx_values[[0, -1]]
print(idx_values)
# array([3, 5, 7], dtype=int64)
idx_values returns all the index values meeting your condition. You can then access the smallest and largest index positions.
print(min_idx, max_idx)
# (3, 7)