Erin's equation

Erin's equation is a mathematical function which computes the number that is the same order of magnitude as a given number, but with only one significant digit.

Python sourcecode

1  def erin(x):
2      from math import *
3      t = pow(10, floor(log10(x)))
4      return t * floor(x/t)

Fortran sourcecode

1  pure function erin(x) result(m)
2   use iso_fortran_env, only: wp => real64
3   implicit none
4   real(wp),intent(in) :: x
5   real(wp) :: m,t
6   t = 10**floor(log10(x))
7   m = t * floor(x/t)
8  end function erin

Example

erin(9876.54321) = 9000.0

See also

• Potter's equation