FUNCTION hist,f,scale=scale,n=n
  max=max(f,min=min)
  if n_elements(n) eq 0 then n=100
  bin=(max-min)/n
; print,'min =',min,'  max =',max
  h=histogram(f,bin=bin)
  scale=min+bin*findgen(n_elements(h))
  return,h
end

PRO ploghist,f,title=title,xtitle=xtitle,n=n,chars=chars,oplt=oplt,line=line,$
    psym=psym,xrange=xrange,yrange=yrange,ytitle=ytitle,prob=prob

; histogram
  y=hist(f,scale=x,n=n)

; parameters
  if n_elements(title) eq 0 then title=' '
  if n_elements(xtitle) eq 0 then xtitle=' '
  if n_elements(ytitle) eq 0 then ytitle=' '
  if n_elements(chars) eq 0 then chars=1.0
  if n_elements(line) eq 0 then line=0
  if n_elements(psym) eq 0 then psym=10
  if n_elements(xrange) eq 0 then xrange=[min(x),max(x)]

; probability
  if keyword_set(prob) then y=y/float(total(y))*n/abs(x(n)-x(0))
; if n_elements(prob) ne 0 then begin
;   s=size(f)
;   if(s(0) eq 1) then n=s(1)*1.
;   if(s(0) eq 2) then n=s(1)*1.*s(2)
;   if(s(0) eq 3) then n=s(1)*1.*s(2)*1.*s(3)
;   if(s(0) eq 4) then n=s(1)*1.*s(2)*1.*s(3)*1.*s(4)
;   y=y/n
; endif
  if n_elements(yrange) eq 0 then yrange=[min(y),max(y)]

; plot
  if n_elements(oplt) eq 0 then begin
;   plot_oo,x,y,title=title,xtitle=xtitle,chars=chars,line=line,psym=psym,$
    plot_io,x,y,title=title,xtitle=xtitle,chars=chars,line=line,psym=psym,$
    xrange=xrange,yrange=yrange,ytitle=ytitle
  endif else begin
    oplot,x,y,psym=psym,line=oplt
  endelse
END