Generate 3 different random number in Python

Question

I am beginner in python. I want to generate 3 set of different number within specified range using numpy.random.randint in python3. (F.Y.I -> Want to implement K-Means)

I am using this code

# Number of clusters
k = 3
# X coordinates of random centroids
C_x = np.random.randint(38.8, 39.4, size=k)
# Y coordinates of random centroids
C_y = np.random.randint(-77.5,-76.5, size=k)
C = np.array(list(zip(C_x, C_y)), dtype=np.float32)
print(C)

But each iteration gives me same set of values

[[ 38. -77.]
 [ 38. -77.]
 [ 38. -77.]]

Where am I going wrong?

Your only integer in the range 38 (inclusive) and 39 (non inclusive) is 38, that's why you always get 38, same for the second ranges - your ranges do not allow anything else as they are not inclusive. — dmitryro
– dmitryro, Commented Feb 10, 2018 at 19:54

Martijn Pieters · Accepted Answer · 2018-02-10 19:53:37Z

2

The randint() function operates on integers; your floats are floored to integers before taking the random value. Because the second values is exclusive, you are producing a range of just one value each.

Either pass in integers for the low and high values (and pick a larger range), or use one of the distribution functions. The numpy.random.uniform() function is fine for your needs, I presume?

>>> C_x = np.random.uniform(38.8, 39.4, size=k)
>>> C_y = np.random.uniform(-77.5,-76.5, size=k)
>>> np.array(list(zip(C_x, C_y)), dtype=np.float32)
array([[ 39.04865646, -76.83393097],
       [ 39.06672668, -76.70361328],
       [ 39.35120773, -77.00741577]], dtype=float32)

answered Feb 10, 2018 at 19:53

Martijn Pieters

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Comments

Omkar · Accepted Answer · 2018-02-10 20:09:04Z

1

I used numpy.random.uniform

# Number of clusters
k = 3
# X coordinates of random centroids
C_x = np.random.uniform(38.8, 39.4, size=k)
# Y coordinates of random centroids
C_y = np.random.uniform(-77.5,-76.5, size=k)
C = np.array(list(zip(C_x, C_y)), dtype=np.float32)
print(C)

and it worked.

[[ 38.88471603 -77.37638855]
 [ 38.99485779 -76.99333954]
 [ 38.97389603 -77.27649689]]

answered Feb 10, 2018 at 20:09

Omkar

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