Mode

Mode

PROBLEM

The problem is to determine the most frequently occuring value, called the mode, of a sorted array.

ALGORITHM

The elegant algorithm used to compute the mode was invented by Griffits.

IMPLEMENTATION

Unit: internal function

Global variables: the input sorted array A. of arbitrary elements

Parameter: a positive integers N - number of elements in A.

Returns: Couple of values Mode and Frequence of mode separated by blanks.

MODE: procedure expose A.
parse arg N
Mode = A.1; Frequence = 1
do J = 2 to N
  JmFrequence = J - Frequence
  if A.J = A.JmFrequence
    then do
      Frequence = Frequence + 1; Mode = A.J
    end
end
return Mode Frequence

EXAMPLE

N = 5
A.1 = 1; A.2 = 2; A.3 = 2; A.4 = 3; A.5 = 5
say MODE(N)
exit
MODE: procedure expose A.
...

displays 2 2

Literature
Gehani N., Ada - An Advanced Introduction

Prentice-Hall, Inc. Englewood Cliffs, New Jersey 1983