Task: Averages_Mode

C: #include <stdio.h>
#include <stdlib.h>

typedef struct { double v; int c; } vcount;

int cmp_dbl(const void *a, const void *b)
{
	double x = *(const double*)a - *(const double*)b;
	return x < 0 ? -1 : x > 0;
}

int vc_cmp(const void *a, const void *b)
{
	return ((const vcount*)b)->c - ((const vcount*)a)->c;
}

int get_mode(double* x, int len, vcount **list)
{
	int i, j;
	vcount *vc;

	
	qsort(x, len, sizeof(double), cmp_dbl);

	
	for (i = 0, j = 1; i < len - 1; i++, j += (x[i] != x[i + 1]));

	*list = vc = malloc(sizeof(vcount) * j);
	vc[0].v = x[0];
	vc[0].c = 1;

	
	for (i = j = 0; i < len - 1; i++, vc[j].c++)
		if (x[i] != x[i + 1]) vc[++j].v = x[i + 1];

	
	qsort(vc, j + 1, sizeof(vcount), vc_cmp);

	
	for (i = 0; i <= j && vc[i].c == vc[0].c; i++);

	return i;
}

int main()
{
	double values[] = { 1, 3, 6, 6, 6, 6, 7, 7, 12, 12, 12, 12, 17 };
#	define len sizeof(values)/sizeof(double)
	vcount *vc;

	int i, n_modes = get_mode(values, len, &vc);

	printf("got %d modes:\n", n_modes);
	for (i = 0; i < n_modes; i++)
		printf("\tvalue = %g, count = %d\n", vc[i].v, vc[i].c);

	free(vc);
	return 0;
}










Fortran: program mode_test
  use Qsort_Module only Qsort => sort
  implicit none

  integer, parameter    :: S = 10
  integer, dimension(S) :: a1 = (/ -1, 7, 7, 2, 2, 2, -1, 7, -3, -3 /)
  integer, dimension(S) :: a2 = (/  1, 1, 1, 1, 1, 0, 2, 2, 2, 2 /)
  integer, dimension(S) :: a3 = (/  0, 0, -1, -1, 9, 9, 3, 3, 7, 7 /)

  integer, dimension(S) :: o
  integer               :: l, trash

  print *, stat_mode(a1)

  trash = stat_mode(a1, o, l)
  print *, o(1:l)
  trash = stat_mode(a2, o, l)
  print *, o(1:l)
  trash = stat_mode(a3, o, l)
  print *, o(1:l)

contains

  
  
  
  
  
  
  integer function stat_mode(a, others, otherslen, ok)
    integer, dimension(:), intent(in) :: a
    logical, optional, intent(out)    :: ok
    integer, dimension(size(a,1)), optional, intent(out) :: others
    integer, optional, intent(out)    :: otherslen

    
    
    
    integer, dimension(size(a, 1)) :: ta, freq, idx
    integer                        :: rs, i, tm, ml, tf

    if ( present(ok) ) ok = .false.

    select case ( size(a, 1) )
    case (0)  
       return
    case (1)
       if ( present(ok) ) ok = .true.
       stat_mode = a(1)
       return
    case default
       if ( present(ok) ) ok = .true.
       ta = a         
       call sort(ta)  
       freq = 1
       idx = 0
       rs = 1         
       
       do i = 2, size(ta, 1)
          if ( ta(i-1) == ta(i) ) then
             freq(rs) = freq(rs) + 1
          else
             idx(rs) = i-1
             rs = rs + 1
          end if
       end do
       idx(rs) = i-1
         
       ml = maxloc(freq(1:rs), 1)  
       tf = freq(ml)               
       tm = ta(idx(ml))            

       
       if ( present(others) ) then
          i = 1
          others(1) = tm
          do
             freq(ml) = 0
             ml = maxloc(freq(1:rs), 1)
             if ( tf == freq(ml) ) then 
                i = i + 1               
                others(i) = ta(idx(ml))
             else
                exit
             end if
          end do
                
          if ( present(otherslen) ) then
             otherslen = i
          end if

       end if
       stat_mode = tm
    end select

  end function stat_mode

end program mode_test