x = (/1,1,1,2,2,3,3,3,3,3,4,4,4,5,5,5,5,6,8,9,9,9,10/)   ; 18 values total

  wks = gsn_open_wks("x11","histo")       ; 9 bars of values 3,2,5,3,4,1,0,1,4

  res = True

  res@tiMainString = str_join(""+x,",")

;---Let gsn_histogram pick the bin intervals to use.
  plot=gsn_histogram(wks,x,res)

;---Specify the bin intervals to use.
  res@gsnHistogramBinIntervals  = (/1,5,8,10/)   ; 3 bars of values 13, 5 and 5
  plot = gsn_histogram(wks,x,res)

;---Count the number of values exactly equal to a value, rather than a range of values.
  delete(res@gsnHistogramBinIntervals)
  res@gsnHistogramDiscreteBinValues  = ispan(1,5,1)
  plot = gsn_histogram(wks,x,res)