Changing FillValues

hello,

sorry, I used to know how to do this, but I have forgotten and I can't
find the solution on the search NCL pages.

I have a variable (cloudsat data) that has the FillValue defined as
zero, while missing values have a variety of negative value flags (e.g.
-3333, -4444 and so on).

I wanted to set the fillvalue to -3333, and then set all negative
numbers to the fillvalue, while leaving the zeros unchanged (i.e. they
are not really missing...)

I did this

;
; set all negative values to missing values.
;
    var@_FillValue=integertoshort(-3333)
    var=where(var.lt.0,var@_FillValue,var)

but the first line changes all the Zeros to -3333...

How can I "define" the missing/fillvalue as -3333 without changing the
zeros in the field array?

Many thanks,

Adrian

-- 
Adrian Tompkins          | Earth System Physics
+39 040 2240579 (office) | ICTP (UNESCO-IAEA)
+39 040 2240449 (fax)    | Strada Costiera 11
www.ictp.it              | 34151 Trieste, Italy
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