function levs,values,nlevelso

nlevels=nlevelso
;------------------------------------------
; a function that returns a vector of contour levels such that the contours 
; appear evenly throughout the data
;------------------------------------------
tryagain:
pass=(values ne 99999.0)*(finite(values))
goodind=where(pass)
values=values(goodind)
values=float(values)
sortdata=values(uniq(values,sort(values)))
narg=total(sortdata ne 99999.0)
levsubs=floor(findgen(nlevels)*(narg/nlevels))
levels=sortdata(levsubs)
sz=size(uniq(levels))

blow=min(levels)*0.9*(min(levels) gt 0)+min(levels)*1.1*(min(levels) lt 0)$
+(min(levels) eq 0.)*(-0.1)
bhi=max(levels)*1.1*(max(levels) gt 0)+max(levels)*0.9*(max(levels) lt 0)$
+(max(levels) eq 0.)*(0.1)

if sz(1) eq nlevels then goto,haha

if min(levels) eq max(levels) then begin
levels=max(levels)
return,interpol([blow,levels,bhi],nlevels)
endif


nlevels=sz(1)

print,'actual levels=',nlevels

goto,tryagain

haha:

levels=interpol([blow,levels,bhi],nlevelso)
check=where(deriv(levels) gt 1.e-7)
new=n_elements(levels)-(total(deriv(levels) le 1.e-7))
levelsnew=fltarr(new)
levelsnew=levels(check)
levels=levelsnew
levels=levels(uniq(levels))
return,interpol([blow,levels,bhi],nlevelso)
end