;+
;
; @file_comments
; We give a min and a max, and the procedure send back
; the good contour interval and labels's value.
;
; @categories
; Graphics
;
; @param MIN {in}{required} {type=float}
; above what value we want to trace a contour
;
; @param MAX {in}{required} {type=float}
; below what value we want to trace a contour
;
; @param CI {out} {type=real}
; the contour interval. Use it in <proidl>CONTOUR</proidl> with the 
; keyword LEVEL.
;
; @restrictions
; CI is a multiple of the unity in unity log of 10.
; It force the number of contours to be even.
;
; @history
; G. Roullet / aout 99 (gr\@lodyc.jussieu.fr)
;
; @version
; $Id$
;
;-
;
PRO autoscale, min, max, ci
;
  compile_opt idl2, strictarrsubs
;
; Estimation of a first CI, notice the presence of the floor (Inferior round)
; This CI is a multiple of the unity in unity log of 10.
    ci = (max-min)/20.
    ci = 10.^floor(alog10(ci))

    n = 0
    ci0 = ci
;
    coef = [2, 2.5, 5, 10]
;
; We test differents CI (contour intervals), i.e. 1, 2, 2.5, 5 and 10
; until the number of contour is inferior to 30.
;
    WHILE ceil((max-min)/ci) GE 30 DO BEGIN
          ci = ci0*coef[n]
          n = n+1
    ENDWHILE

    min = floor(min/ci/2)*ci*2
    max = ceil(max/ci/2)*ci*2

    nlevels = round((max-min)/ci)

;
;  We force the number of contour to be even
;
    IF nlevels MOD 2 EQ 1 THEN BEGIN
          nlevels = nlevels+1
          max = max+ci
    END
END