Get floating random numbers between -2 and 2 only using random.random in numpy?

Question

I would like to get a random floating-point value between -2 and +2. The best I could do is:

my_array = [-1, 1]
change_sign = []
for i in range(6):
  change_sign.append(my_array[np.random.randint(low=0, high=2)] * 2)
print(change_sign)
results = np.random.random([6]) * change_sign

Desired output:

[-1.14, -0.25, 0.33, 1.75, 1.99, -0.83]

But I feel like it could be done even more easily. I don't want to use other numpy methods (like uniform), just random and randint.

How could I do that?

Answer 1

np.random.random returns a random float between 0.0 and 1.0

so you can multiply by 4 and subtract 2 so the range would be -2.0 to 2.0

np.random.random(6)*4 - 2
array([ 1.41044053, -0.97521584,  1.55446329, -0.54314241, -1.55691897,
        0.28276924])

Answer 2

To get 'n' (= 10) random numbers between 'a' (= -2) and 'b' (= 2) use this formula:

n = 10
a = -2
b = 2

r = a + (b - a) * numpy.random.random(n)

Result:

array([ 0.29379447,  1.0017837 ,  0.46310858, -1.79242304,  1.04047713,
       -0.71521254,  0.32970214,  1.16248318, -1.12456574, -0.47470759])