Re: Question about Making NaN..

[Jaison Kurian <jaison@xxxxxxxxxxxxxxxxxx>]

Hi Jordan & Jammal Tanclei,
                            The two variable method will make all values .GE. 0 
missing values ( I think the expression "missing_value" wiil be more appropriate
than "NAN" in the context of Ferret & netCDF). 

    yes? let dat  = {30,29,28.5,31,0,26,39,0,-31}
    yes? let var1 = if dat lt 0.0 then dat
    yes? let var  = if var1 gt 0.0 then dat else var1
    yes? list var
                 VARIABLE : IF VAR1 GT 0.0 THEN DAT ELSE VAR1
                 SUBSET   : 9 points (X)
     1   / 1:   ....
     2   / 2:   ....
     3   / 3:   ....
     4   / 4:   ....
     5   / 5:   ....
     6   / 6:   ....
     7   / 7:   ....
     8   / 8:   ....
     9   / 9: -31.00
    yes?    

If you want to convert only "0.0" to missing value then ;

  method.1 : set the "bad" (ie. missing ) value for the variable to 0.0
             (This will not alter the "effect of" a previous missing_value, if
               exists)
              
    
    yes? let dat  = {30,29,28.5,31,0,26,39,0,-31}
    yes? set var/bad=0.0 dat
    yes? list dat
                 VARIABLE : {30,29,28.5,31,0,26,39,0,-31}
                 SUBSET   : 9 points (X)
     1   / 1:  30.00
     2   / 2:  29.00
     3   / 3:  28.50
     4   / 4:  31.00
     5   / 5:   ....
     6   / 6:  26.00
     7   / 7:  39.00
     8   / 8:   ....
     9   / 9: -31.00
    yes?     

  method.2 : Define a new variable so that "0.0" will be missing value

    yes? let dat  = {30,29,28.5,31,0,26,39,0,-31}   
    yes? let dat1 = IF dat LT 0 OR dat GT 0 THEN dat
    yes? list dat1
                 VARIABLE : IF DAT LT 0 OR DAT GT 0 THEN DAT
                 SUBSET   : 9 points (X)
     1   / 1:  30.00
     2   / 2:  29.00
     3   / 3:  28.50
     4   / 4:  31.00
     5   / 5:   ....
     6   / 6:  26.00
     7   / 7:  39.00
     8   / 8:   ....
     9   / 9: -31.00
    yes?


 Hope this helps

 With Regards

 Jaison


On Sat, 25 Sep 2004, Jordan Dawe wrote:

> jammal Tanclei wrote:
> 
> > Hi, Ferret Users.
> >  
> > I need to change the value of 0.0 to "NaN" because after that I'm 
> > going to use function of @FLN to do interpolation at the boundary of land.
> >  
> > Is there anybody to help me?
> >  
> 
> You can do something like this:
> 
> let var1 = if data lt 0.0 then data
> let var = if var1 gt 0.0 then data else var1
> 
> This should leave 0.0 undefined in var.
> 
> Jordan
> 

-- 
___________________________________________________

    Jaison Kurian                           
    Centre for Atmospheric and Oceanic Sciences
    Indian Institute of Science
    B A N G A L O R E   560 012
    Ph: +91-80-3942505
        +91-80-3600450
    Fax:+91-80-3600865
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