Python Notes: RMS Demo

  1. The information presented here is intended for educational use.
  2. The information presented here is provided free of charge, as-is, with no warranty of any kind.
  3. Edit: 2025-04-05

RMS Demo (the code)

#!/bin/python3.9
'''
title  : rms_demo_100.py
author : Neil Rieck
created: 2025-04-06
notes  :
1) just playing around with some electrical stuff here
2) RMS (root-mean-square) is similar to area under a curve
   which is necessary when comparing AC to DC
3) a simpler program could be written without a numpy array,
   but I did it this way just to show how to do it.
4) np.empty creates a uninitialized array
5) np.zeros creates an initialized array
'''

import math
import numpy as np
import sys

angles = 360
# arr1d = np.empty([angles], dtype = float)
arr1d = np.zeros([angles], dtype = float)

def method1():
    # no sqare or square root here (so not RMS)
    global arr1d
    for x in range(angles):
        y = math.sin(math.radians(x))
        arr1d[x] = abs(y)
    # print(arr1d)
    total = np.sum(arr1d)
    print("-i-method1  : ", total / angles)

def method2():
    global arr1d
    for x in range(angles):
        y = math.sin(math.radians(x))
        a = abs(y)
        arr1d[x] = a * a        # square
    # print(arr1d)
    total1 = np.sum(arr1d)
    total2 = total1 / angles
    total3 = math.sqrt(total2)  # square root
    print("-i-method2  : ", total3)

def ref():
    print("-i-reference: ", math.sin(math.radians(45)))

def main():
    script = sys.argv[0]
    print("-i-script: ", script)
    method1()
    method2()
    ref()
    print("-i-exiting")

#
#   catch-all
#
if __name__ == '__main__':
    main()

# this is the last line

Output on Linux

$ ./rms_demo_100.py
-i-script:  ./rms_demo_100.py
-i-method1  :  0.6366036118294979
-i-method2  :  0.7071067811865476
-i-reference:  0.7071067811865475
-i-exiting
$

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 Neil Rieck
 Waterloo, Ontario, Canada.