Top Five Numbers from a list

Hello everyone,

I have a list of integers representing the number of times a number occurs.

such as: ( 4 6 2 8 10 13 12 3 9 1)

For instance the number 1 occured 4 times, number 2 occured 6 times, and the number 3 occured 2 times and so fourth where the first item in the list reprsents 1 and so on. What I am trying to do is retrieve the top five numbers that occured the most. In this case it would be: 6 @ 13 occurrences, 7 @ 12 occurrences, 5 @ 10 occurrences, 9 @ 9 occurrences and 4 @ 8 occurrences. I am trying to create a function that given a list would return these top five numbers in a constructed list. ie ((6 . 13)(7 . 12)(5 . 10)(9 . 9)(4 . 8 ))

Any help would be greatly appreciated.

Regards

Hippe013

Here is a start ...

(setq a (list 4 6 2 8 10 13 12 3 9 1))
(cons (nth 1 a) 13)
(cons (nth 8 a) 9)

Regards,

Tharwat

Thinking out loud here...

Maybe use the (apply) and (max) functions to return the maximum value and it's place, then remove this value from the list and repeat, building the cons list each iteration....?

Not heavily tested but maybe it will give you some ideas

(vl-load-com)

;Input 	-	List of numbers
;Retval	-	List of dotted pairs sorted by occurence
;Sample - 	(sort_by_occurence (list 1 2 1 1 1 2 3 2 2 2 2 2 3 4 55 1 3 4)) ->
;		((2 . 7) (1 . 5) (3 . 3) (4 . 2) (55 . 1))
;		2 occurs 7 times, 1 occurs 5 times etc.....


(defun sort_by_occurence (<list> / tempList)
 
 (foreach n <list>
(setq tempList
	(if
	  (setq item (assoc n tempList))

	  (subst  (cons (car item) (1+ (cdr item))) item tempList)
	  (append tempList (list (cons n 1))))))

  (vl-sort tempList
   (function (lambda (e1 e2)
	       (> (cdr e1) (cdr e2)))))
 )

Regards

Jammie

Kind of a kudge, but it's a start:

[b][color=BLACK]([/color][/b]defun datom [b][color=FUCHSIA]([/color][/b]at lst / nlst[b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]and [b][color=NAVY]([/color][/b]listp lst[b][color=NAVY])[/color][/b]
       [b][color=NAVY]([/color][/b]> [b][color=MAROON]([/color][/b]length lst[b][color=MAROON])[/color][/b] 0[b][color=NAVY])[/color][/b]
       [b][color=NAVY]([/color][/b]foreach a lst
         [b][color=MAROON]([/color][/b]if [b][color=GREEN]([/color][/b]not [b][color=BLUE]([/color][/b]equal at a[b][color=BLUE])[/color][/b][b][color=GREEN])[/color][/b]
             [b][color=GREEN]([/color][/b]setq nlst [b][color=BLUE]([/color][/b]cons a nlst[b][color=BLUE])[/color][/b][b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b][b][color=NAVY])[/color][/b][b][color=FUCHSIA])[/color][/b]
  [b][color=FUCHSIA]([/color][/b]reverse nlst[b][color=FUCHSIA])[/color][/b][b][color=BLACK])[/color][/b]

 [b][color=BLACK]([/color][/b]setq tmp nil rl nil tl nil[b][color=BLACK])[/color][/b]

 [b][color=BLACK]([/color][/b]setq l [b][color=FUCHSIA]([/color][/b]list 4 6 2 8 10 13 12 3 9 1[b][color=FUCHSIA])[/color][/b]
      tl l
       i 1[b][color=BLACK])[/color][/b]

 [b][color=BLACK]([/color][/b]while [b][color=FUCHSIA]([/color][/b]> [b][color=NAVY]([/color][/b]length tl[b][color=NAVY])[/color][/b] 1[b][color=FUCHSIA])[/color][/b]
        [b][color=FUCHSIA]([/color][/b]setq tmp [b][color=NAVY]([/color][/b]cons [b][color=MAROON]([/color][/b]cons [b][color=GREEN]([/color][/b]car tl[b][color=GREEN])[/color][/b] i[b][color=MAROON])[/color][/b] tmp[b][color=NAVY])[/color][/b]
               tl [b][color=NAVY]([/color][/b]cdr tl[b][color=NAVY])[/color][/b]
                i [b][color=NAVY]([/color][/b]1+ i[b][color=NAVY])[/color][/b][b][color=FUCHSIA])[/color][/b][b][color=BLACK])[/color][/b]

 [b][color=BLACK]([/color][/b]repeat 5
   [b][color=FUCHSIA]([/color][/b]setq mi [b][color=NAVY]([/color][/b]apply 'max l[b][color=NAVY])[/color][/b]
         ma [b][color=NAVY]([/color][/b]assoc mi tmp[b][color=NAVY])[/color][/b]
         rl [b][color=NAVY]([/color][/b]cons [b][color=MAROON]([/color][/b]cons [b][color=GREEN]([/color][/b]cdr ma[b][color=GREEN])[/color][/b] [b][color=GREEN]([/color][/b]car ma[b][color=GREEN])[/color][/b][b][color=MAROON])[/color][/b] rl[b][color=NAVY])[/color][/b]
          l [b][color=NAVY]([/color][/b]datom mi l[b][color=NAVY])[/color][/b][b][color=FUCHSIA])[/color][/b][b][color=BLACK])[/color][/b]
 [b][color=BLACK]([/color][/b]setq rl [b][color=FUCHSIA]([/color][/b]reverse rl[b][color=FUCHSIA])[/color][/b][b][color=BLACK])[/color][/b]

 [b][color=BLACK]([/color][/b]prin1 tmp[b][color=BLACK])[/color][/b]
 [b][color=BLACK]([/color][/b]princ[color=#2f4f4f]"\n"[/color][b][color=BLACK])[/color][/b]
 [b][color=BLACK]([/color][/b]prin1 rl[b][color=BLACK])[/color][/b]

HTH -David

Another:

(defun Top5 ( lst / LM:ListOccurrences LM:GetFirstN )
 (vl-load-com)
 ;; © Lee Mac 2010

 (defun LM:ListOccurrences ( lst )
   ;; © Lee Mac 2010
   (if lst
     (cons
       (cons (car lst)
         (- (length lst) (length (vl-remove (car lst) lst)))
       )
       (LM:ListOccurrences (vl-remove (car lst) lst))
     )
   )
 )

 (defun LM:GetFirstN ( lst n )
   ;; © Lee Mac 2010
   (if (and lst (< 0 n))
     (cons (car lst) (LM:GetFirstN (cdr lst) (1- n)))
   )
 )

 (LM:GetFirstN
   (vl-sort (LM:ListOccurrences lst) '(lambda ( a b ) (> (cdr a) (cdr b)))) 5
 )
)