I am trying to create a matrix in a random way in the intervals [-5,-1] and [1,5]. How can I create a matrix taking into account the intervals (no 0 values) with random values?
I tried to do it with randint
of numpy and with piecewise
. In the first case it is not posible to indicate 2 intervals and in the second case the random number generated when the value is close to 0 (bigger than -1 and lower than 1) is always the same.
x=np.random.randint(-5,5,(2,3))
np.piecewise(x, [x <= 1, x >=-1 ], [np.random.randint(-5,-1), np.random.randint(1,5)])
I would like to have a matrix in this way with no 0 values:
[-2,-3,-1
1,-2, 3]
You can create a random positive matrix and multiply it element wise by a random sign:
np.random.randint(1,6,(2,3))*np.random.choice([-1,1],(2,3))
Keep in mind that this only works if the interval is even around 0
, e.g. (-6,6)
(0
excluded).
One option is to simply "remap" the value 0 to one of the bounds:
import numpy as np
np.random.seed(100)
x = np.random.randint(-5, 5, (4, 8))
x[x == 0] = 5
print(x)
# [[ 3 3 -2 2 2 -5 -1 -3]
# [ 5 -3 -3 -3 -4 -5 3 -1]
# [-5 4 1 -3 -1 -4 5 -2]
# [-1 -1 -2 2 -4 -4 2 2]]
Or you can use np.random.choice
:
import numpy as np
np.random.seed(100)
np.random.choice(list(range(-5, 0)) + list(range(1, 6)), size=(4, 8))
print(x)
# [[ 3 3 -2 2 2 -5 -1 -3]
# [ 5 -3 -3 -3 -4 -5 3 -1]
# [-5 1 -3 -1 -4 5 -2 -1]
# [-1 -2 2 -4 -4 2 2 -5]]
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