To get a logarithmic array of 1000 until 1000000000 with 23 points I wrote this code in Python:
import numpy as np
x4 = np.logspace(start=1000, stop=1000000000, num=23, base=10)
print(x4)
The results where:
[inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf inf]
How do you solve this problem and what did I do wrong in my code?
np.logspace is not doing what you think it's doing. You are expecting the effect of np.geomspace:
10**np.linspace(np.log(1000), np.log10(1000000000), 23)
In fact, you are getting
10**np.linspace(1000, 1000000000, 23)
From the docs:
In linear space, the sequence starts at
base ** start(base to the power of start) and ends withbase ** stop(see endpoint below).
So you probably want
np.logspace(3, 9, num=23, base=10)
Or alternatively,
np.geomspace(10**3, 10**9, 23)
The exact reason for the result can be seen with np.finfo:
>>> np.finfo(np.float_)
finfo(resolution=1e-15, min=-1.7976931348623157e+308, max=1.7976931348623157e+308, dtype=float64)
Since 10**1000 > 1.7976931348623157e+308, inf is just a signal of the expected overflow.
I think you misunderstood what logspace does. It gives you the powers, starting with base**start, which in your case is 10**1000. So in your case:
out = np.logspace(start=3, stop=9, num=23, base=10)
And test:
plt.plot(out)
plt.yscale('log')
Output:
