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Re: [ferret_users] Ferret 6.3: lev=(lo,hi,delta) yields a hi+delta contour

Hi Ryo,
Thanks for the report and the example. I'm sure you are correct that this is due to numerical precision in the calculation; in fact I only see the incorrect extra level running the 32-bit version of Ferret, with the 64-bit linux executable I don't.

We'll take a look at it.


Ryo Furue wrote:
Hi Ferreters,

I found that in Ferret 6.3, lev=(lo,hi,delta) sometimes gives
a hi+delta contour:

  $ ferret
          NOAA/PMEL TMAP
          FERRET v6.3
          Linux(g77) 2.4.21-32 - 09/29/09
           4-Nov-09 14:26
  set mode grat:dash
  keymark 1
  yes? set data coads_climatology
  yes? contour/hlimits=160:180/vlimits=40:60/lev=(3,3.9,0.1)/l=1 sst

In this example, the contour levels include 4.0 .  On Ferret v6.2,
the maximum contour level is 3.9 .

My wild guess is that this is because "0.1" is actually 0.0999999
or so in single precision so that 3 + 0.1*9 < 3.9 . . . .


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