Producing a geometric sequence using NumPy

Question

I'm trying to produce a geometric sequence, something similar to 1, 2, 4, 8...

I have the following code:

import numpy as np

lower_price = 1
upper_price = 2
total_grids = 10

grid_box = np.linspace(lower_price , upper_price, total_grids, retstep=True)

print(grid_box)

This outputs:

(array([1.        , 1.11111111, 1.22222222, 1.33333333, 1.44444444,
       1.55555556, 1.66666667, 1.77777778, 1.88888889, 2.        ]), 0.1111111111111111)

This code creates an arithmetic, rather than a geometric sequence. How can I fix this code to produce the latter as opposed to the former?

Answer 1

You're looking for np.logspace, not np.linspace:

For example,

# Lower bound is 2**0 == 1
# Upper bound is 2**10 == 1024
np.logspace(0, 10, 10, base=2)

outputs:

[1.00000000e+00 2.16011948e+00 4.66611616e+00 1.00793684e+01
 2.17726400e+01 4.70315038e+01 1.01593667e+02 2.19454460e+02
 4.74047853e+02 1.02400000e+03]

---

If you're trying to get 10 values between 1 and 2, use:

# Lower bound is 2**0 == 1
# Upper bound is 2**1 == 2
np.logspace(0, 1, 10, base=2)

Answer 2

'percentage' gives the % increment between each values. You can see that it remains constant for constant total_grids and changes only if you change it.

import numpy as np

lower_price = 10
upper_price = 2000
total_grids = 10

grid_box = np.linspace(lower_price , upper_price, total_grids, retstep=True)

full_range = upper_price - lower_price
correctedStartValue = grid_box[0][1] - lower_price
percentage = (correctedStartValue * 100) / full_range 

print(grid_box)
print(percentage)