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

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

Fortran sourcecode

pure function erin(x) result(m)
 use iso_fortran_env, only: wp => real64
 implicit none
 real(wp),intent(in) :: x
 real(wp) :: m,t
 t = 10**floor(log10(x))
 m = t * floor(x/t)
end function erin

Example

erin(9876.54321) = 9000.0

See also

• Potter's equation