Intro
I have some range of frequencies that goes from freq_start_hz = X to freq_stop_hz = Y.
I am trying to logarithmically (base 10) space out samples between the range [freq_start_hz, freq_stop_hz], based on a number of samples per decade (num_samp_per_decade), inclusive of the endpoint.
I noticed numpy has a method logspace (link) which enables you to create logarithmic divisions of some range base ** start to base ** stop based on a total number of samples, num.
Can you help me create Python code that will create even logarithmic spacing per decade?
Example
freq_start_hz = 10, freq_stop_hz = 100, num_samp_per_decade = 5
This is easy, since it's just one decade. So one could create it using the following:
import numpy as np
from math import log10
freq_start_hz = 10
freq_stop_hz = 100
num_samp_per_decade = 5
freq_list = np.logspace(
start=log10(freq_start_hz),
stop=log10(freq_stop_hz),
num=num_samp_per_decade,
endpoint=False,
base=10,
)
freq_list = np.append(freq_list, freq_stop_hz) # Appending end
print(freq_list.tolist())
Output is [10.0, 17.78279410038923, 31.622776601683793, 56.23413251903491, 100.0]
Note: this worked nicely because I designed it this way. If freq_start_hz = 8, this method no longer works since it now spans multiple decades.
Conclusion
I am hoping somewhere out there, there's a premade method in math, numpy, another scipy library, or some other library that my internet searching hasn't turned up.
Calculate the number of points based on the number of decades in the range.
from math import log10
import numpy as np
start = 10
end = 1500
samples_per_decade = 5
ndecades = log10(end) - log10(start)
npoints = int(ndecades) * samples_per_decade
#a = np.linspace(log10(start), log10(end), num = npoints)
#points = np.power(10, a)
points = np.logspace(log10(start), log10(end), num=npoints, endpoint=True, base=10)
print(points)