Numpy linspace to create array by using start stop and number of elements

Numpy

numpy.linspace(start,stop,num=50,endpoint=True,retstep=False,dtype=None,axis=0)

Return evenly spaced numbers over the specified num (evenly spaced intervals )

`start`	number, Start value of the sequence
`stop`	number, Stop value of the sequence
`num`	integer ( optional ) default = 50 , number of equal interval samples.
`dtype`	data type of output, Optional
`endpoint`	Boolean, default is True, To use stop value as last element or not
`retstep`	Boolean, default is False, if True it returns the STEP value used along with the samples.
`axis`	int, Optional , To use start and stop arrays to create axis of output.

Examples

We will use all above options to create ndarray using linspace()

import numpy as np
print(np.linspace(2,10))

Default value of num ( number of samples ) is 50. We have specified here start=2 and stop=10 so we are getting 50 samples of evenly spaced numbers.

[ 2.          2.16326531  2.32653061  2.48979592  2.65306122  2.81632653
  2.97959184  3.14285714  3.30612245  3.46938776  3.63265306  3.79591837
  3.95918367  4.12244898  4.28571429  4.44897959  4.6122449   4.7755102
  4.93877551  5.10204082  5.26530612  5.42857143  5.59183673  5.75510204
  5.91836735  6.08163265  6.24489796  6.40816327  6.57142857  6.73469388
  6.89795918  7.06122449  7.2244898   7.3877551   7.55102041  7.71428571
  7.87755102  8.04081633  8.20408163  8.36734694  8.53061224  8.69387755
  8.85714286  9.02040816  9.18367347  9.34693878  9.51020408  9.67346939
  9.83673469 10.        ]

Let us specify num ( num = 5 )

print(np.linspace(2,10,5)) # [ 2.  4.  6.  8. 10.]

In above code, start=2, stop=10 and num=5. We are getting 5 elements starting from 2 and ending at 10 with an equal increment of 2.

endpoint

In above code we have used included the stop value in our element ( i.e 10 ) . This is because default value of option endpoint=True. Let us change it to False and see the result.

print(np.linspace(2,10,5,endpoint=False)) # [2.  3.6 5.2 6.8 8.4]

Now the stop value 10 is not included in our output. Now the increment is adjusted to 1.6 to return 5 equal incremental elements in our output.

retstep

We can get the step value used by numpy to create the array by using retstep=True. The option retstep takes Boolean value and its default value is False.

print(np.linspace(2,10,5,retstep=True))
y=np.linspace(2,10,5,retstep=True)
print(y[1])

Output

(array([ 2.,  4.,  6.,  8., 10.]), 2.0)
2.0

dtype

We can specify the option dtype to get the data we want.

print(np.linspace(2,10,5,dtype=np.int8)) # [ 2  4  6  8 10]
print(np.linspace(2,10,5,dtype=np.int32)) # [ 2  4  6  8 10]
print(np.linspace(2,10,5,dtype=np.float)) # [ 2.  4.  6.  8. 10.]

axis

We will use 2-D array to use axis option. Let us start with axis=0, our start and stop values are arrays.

print(np.linspace([2,5],[6,25],5,axis=0))

Output

[[ 2.  5.]
 [ 3. 10.]
 [ 4. 15.]
 [ 5. 20.]
 [ 6. 25.]]

Let us change the axis.

print(np.linspace([2,5],[6,25],5,axis=1))

Output

[[ 2.  3.  4.  5.  6.]
 [ 5. 10. 15. 20. 25.]]

linespace() and arange()

In case of linspace() we give the number of samples ( num ) and internally the increments ( or evenly spaced steps) are decided based on start and stop values.

In case of arange() we give the step value and number of elements are internally decided.

Numpy eye() ones() arange() bincount()

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Numpy linspace()

Examples

endpoint

retstep

dtype

axis

linespace() and arange()

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