bad flag gets reset

[Steve Knox <stevek@xxxxxxxxxxxxxxxxxx>]

Hi,
I'm computing the following and it appears that the missing vlaue defined
in my netcdf file is getting
reset when I compute the ration of @var/@ave. The missingvalue is 1.0000000E+20
but when I compute @var/@ave the bad flag is set to -9.9999998E+33 (= -0.1000E+35)
I would have expected the missing value to remain the same, ie 1.0000000E+20.
Any ideas?
Here's the Netcdf header:

 obs.globe.lan.1901-2000.pre.annual {
dimensions:
        lon = 720 ;
        lat = 360 ;
        time = UNLIMITED ; // (100 currently)
variables:
        float lon(lon) ;
                lon:units = "degrees_east" ;
                lon:valid_min = -180.f ;
                lon:valid_max = 180.f ;
                lon:title = "Longitude" ;
        float lat(lat) ;
                lat:units = "degrees_north" ;
                lat:valid_min = -90.f ;
                lat:valid_max = 90.f ;
                lat:title = "Latitude" ;
        float time(time) ;
                time:units = "years since 1900-01-01" ;
                time:title = "Time" ;
                time:long_name = "Time axis" ;
                time:time_origin = " 1900-01-15 00:00:00" ;
        float pre(time, lat, lon) ;
                pre:units = "mm/month" ;
                pre:long_name = "Precipitation" ;
                pre:missing_value = 1.e+20f 

yes? set region/i=1:1/j=1:1      !look at a grid cell that I know is missing
yes? list/l=1:1/format=(e15.6)  pre[l=@ave]
             VARIABLE : Precipitation (mm/month)
             FILENAME : obs.globe.lan.1901-2000.pre.annual.nc
             BAD FLAG :  1.0000000E+20
             LONGITUDE: 179.8W(-179.8)
             LATITUDE : 89.8S
             TIME     : 02-JUL-1900 14:54 to 02-JUL-1901 20:43 (averaged)
   0.100000E+21  (OK)
yes? list/l=1:1/format=(e12.4)  pre[l=@var]
             VARIABLE : Variance of Precipitation ((mm/month)^2)
             FILENAME : obs.globe.lan.1901-2000.pre.annual.nc
             BAD FLAG :  1.0000000E+20
             LONGITUDE: 179.8W(-179.8)
             LATITUDE : 89.8S
             TIME     : 02-JUL-1900 14:54 to 02-JUL-1901 20:43 (variance)
  0.1000E+21 (OK)
yes? list/l=1:1/format=(e12.4)  pre[l=@var]/pre[l=@ave]
             VARIABLE : PRE[L=@VAR]/PRE[L=@AVE]
             FILENAME : obs.globe.lan.1901-2000.pre.annual.nc
             BAD FLAG : -9.9999998E+33 (aka -0.1000E+35)
             LONGITUDE: 179.8W(-179.8)
             LATITUDE : 89.8S
             TIME     : 02-JUL-1900 14:54 to 02-JUL-1901 20:43
 -0.1000E+35 (NOT OK)

-- 
_________________________
Steve Knox
NREL
Colorado State University
(970)491-1972