utests.py

# BSD-3-Clause 
#
# Copyright 2024 S.A Gilchrist
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#
# Help scripts for testing
#

import numpy as np

def power_law_fit(x,y,cov=False):
  """
    Fit a power law y = A*x^gamma
      
    Parameters:
    -----------
      x: array
        Array of x values
      y: array
        Array of y values

    Returns:
    --------
      gamma: float
        power-law index 
      A: float
        Coefficent of x^gamma
      ev: lambda
        Lambda that returns y = A*x^gamma for the given parameters

  """
  Lx    = np.log10(x)
  Ly    = np.log10(y)
  if(cov):
    p,C    = np.polyfit(Lx,Ly,1,cov=True,full=False)
  else:
    p    = np.polyfit(Lx,Ly,1)
  A     = 10.**p[1]
  ev    = lambda x : A*x**p[0]
 
  if(cov):
    return p[0],A,C,ev 
  else:
    return p[0],A,ev