number sequence in python-CodePudding

How can I make a sequence of numbers -0.05 to 0.05 with 0.002 increment and store it in a vector?

Code

import numpy as np

x=np.zeros(50)

for i in range(-0.05,0.05,0.002):
    x(i)

CodePudding user response：

You can use Numpy's arange():

import numpy as np
np.arange(-0.05,0.05,0.002)

Which creates:

array([-5.00000000e-02, -4.80000000e-02, -4.60000000e-02, -4.40000000e-02,
       -4.20000000e-02, -4.00000000e-02, -3.80000000e-02, -3.60000000e-02,
       -3.40000000e-02, -3.20000000e-02, -3.00000000e-02, -2.80000000e-02,
       -2.60000000e-02, -2.40000000e-02, -2.20000000e-02, -2.00000000e-02,
       -1.80000000e-02, -1.60000000e-02, -1.40000000e-02, -1.20000000e-02,
       -1.00000000e-02, -8.00000000e-03, -6.00000000e-03, -4.00000000e-03,
       -2.00000000e-03,  4.16333634e-17,  2.00000000e-03,  4.00000000e-03,
        6.00000000e-03,  8.00000000e-03,  1.00000000e-02,  1.20000000e-02,
        1.40000000e-02,  1.60000000e-02,  1.80000000e-02,  2.00000000e-02,
        2.20000000e-02,  2.40000000e-02,  2.60000000e-02,  2.80000000e-02,
        3.00000000e-02,  3.20000000e-02,  3.40000000e-02,  3.60000000e-02,
        3.80000000e-02,  4.00000000e-02,  4.20000000e-02,  4.40000000e-02,
        4.60000000e-02,  4.80000000e-02])

You can pass this to around to round to a precision desired:

np.around(np.arange(-0.05,0.05,0.002), 3)

Which makes:

array([-0.05 , -0.048, -0.046, -0.044, -0.042, -0.04 , -0.038, -0.036,
       -0.034, -0.032, -0.03 , -0.028, -0.026, -0.024, -0.022, -0.02 ,
       -0.018, -0.016, -0.014, -0.012, -0.01 , -0.008, -0.006, -0.004,
       -0.002,  0.   ,  0.002,  0.004,  0.006,  0.008,  0.01 ,  0.012,
        0.014,  0.016,  0.018,  0.02 ,  0.022,  0.024,  0.026,  0.028,
        0.03 ,  0.032,  0.034,  0.036,  0.038,  0.04 ,  0.042,  0.044,
        0.046,  0.048])

CodePudding user response：

You can use np.arange() like this:

np.arange(-0.05, 0.05, 0.002)

but it has precision problems around 0, as seen here:

array([-5.00000000e-02, -4.50000000e-02, -4.00000000e-02, -3.50000000e-02,
       -3.00000000e-02, -2.50000000e-02, -2.00000000e-02, -1.50000000e-02,
       -1.00000000e-02, -5.00000000e-03, -2.77555756e-17,  5.00000000e-03,
                                         ^^^^^^^^^^^^^^^

Another approach is to use integers and then divide after, like this:

np.arange(-50, 50, 2) / 1000

which produces:

array([-0.05 , -0.048, -0.046, -0.044, -0.042, -0.04 , -0.038, -0.036,
       -0.034, -0.032, -0.03 , -0.028, -0.026, -0.024, -0.022, -0.02 ,
       -0.018, -0.016, -0.014, -0.012, -0.01 , -0.008, -0.006, -0.004,
       -0.002,  0.   ,  0.002,  0.004,  0.006,  0.008,  0.01 ,  0.012,
        0.014,  0.016,  0.018,  0.02 ,  0.022,  0.024,  0.026,  0.028,
        0.03 ,  0.032,  0.034,  0.036,  0.038,  0.04 ,  0.042,  0.044,
        0.046,  0.048])

CodePudding user response：

It is in fact very simple with NumPy.

Just use np.arange()

import numpy as np

step = 0.002
mini = -0.05
maxi = 0.05

for i in np.arange(mini, maxi step, step):
    print(round(i, 3))

***note This also rounds it to 3 decimal places as other wise it prints with about 46 decimal places.