Missing values

[shenoi@xxxxxxxxxxxxxxxx]

Dear Ferret users,

I came across a strange problem when I used the 'IF' condition to pick the
zonal and meridional components of a vector based on the number of
observations available in a grid.  In one case the vector has a zero value
for one component (ie. v=0.0). In this case when I used the 'IF' condition,
it reports v as missing rather than 0.0. The following will explain the
problem better (see the values reported for 16-Sep, column 2 & 5).

 Column  1: U is U (cm/sec)
 Column  2: V is V (cm/sec)
 Column  3: NOBS is Number of observations
 Column  4: U1 is IF(NOBS GT 10) THEN U
 Column  5: V1 is IF(NOBS GT 10) THEN V
 Column  6: NOBS1 is IF(NOBS GT 10) THEN NOBS
                      U      V   NOBS     U1     V1  NOBS1 
16-JAN      /  1:  -13.0 -13.00  20.00  -13.0 -13.00  20.00
15-FEB      /  2:  -61.0  -3.00  33.00  -61.0  -3.00  33.00
16-MAR      /  3:    7.0   6.00  34.00    7.0   6.00  34.00
16-APR      /  4:  106.0 -13.00  24.00  106.0 -13.00  24.00
16-MAY      /  5:  146.0 -22.00  66.00  146.0 -22.00  66.00
16-JUN      /  6:   60.0 -18.00  51.00   60.0 -18.00  51.00
16-JUL      /  7:   11.0 -17.00  67.00   11.0 -17.00  67.00
16-AUG      /  8:   48.0 -18.00  48.00   48.0 -18.00  48.00
16-SEP      /  9:   67.0   0.00  42.00   67.0   ....  42.00
16-OCT      / 10:   83.0  32.00  36.00   83.0  32.00  36.00
16-NOV      / 11:  150.0 -10.00  40.00  150.0 -10.00  40.00
16-DEC      / 12:   62.0  -2.00  53.00   62.0  -2.00  53.00

Is there any way out for this problem? I want 0.0 when the values are zeros. Not
as 'missing value'. When I compute the annual mean (using @ave)
I get umean with 12 values and vmean with 11 values rather than 12 values
which is incorrect.


Thanks
-satheesh
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Satheesh C. Shenoi 
Physical Oceanography Division,     |  Ph.(office)  : (0091)(832) 226253-56 
National Institute of Oceanography, |          ext 224/400 
Dona Paula, Goa  403 004, India.    |  FAX   : (0091)(832) 22 3340/1360
                                    |  Ph. (home)  (0091)(832) 233453
e-mail : shenoi@csnio.ren.nic.in
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