[ncl-talk] convert the double missing_value to float one

[Dennis Shea]

A comment about netCDF variables. Since NCL variables follow the netCDF
variable model, it holds for NCL variables also.

By rule, the type of the _FillValue should match the type of the variable
with which it is associated.

short variable must have a short _Fillvalue
integer variable ... integer _FillValue
float variable ... float _FillValue
double variable ... double _FillValue

---




On Mon, Jun 19, 2017 at 9:38 AM, Mary Haley <haley at ucar.edu> wrote:

> Beata,
>
> When going from a 'higher' type to a 'lower' type (double to float, for
> example), you need to use the reassignment operator (':=') to force the
> conversion:
>
>   p8 at missing_value := doubletofloat(p8 at missing_value)
>
>    p8 at _FillValue := p8 at missing_value
>
>
> It might be better to use the "totype" function:
>
>
>   p8 at _FillValue := totype(p8 at _FillValue,typeof(p8))
>
>   p8 at missing_value := totype(p8 at missing_value,typeof(p8))
>
>
> --Mary
>
>
>
> On Mon, Jun 19, 2017 at 1:04 AM, Beáta Szabó-Takács <szabo.b at czechglobe.cz
> > wrote:
>
>> Dear NCL Users,
>>
>>
>>
>> I would like to create a taylor_metrics_table where the missing values
>> are denoted by -999. This part of script is:
>>
>>
>>
>>   season    = (/ "DJF","JJA" /)
>>
>>   nSeason   = dimsizes(season)
>>
>>
>>
>>   table     = new ( (/nCase,nSeason,nSource/), typeof(ratio) )
>>
>>   table(0,:,:) = (/CA_bias, CA_biasn/)
>>
>>   table(1,:,:) = (/CB_bias, CB_biasn/)
>>
>>   table(2,:,:) = (/CC_bias, CC_biasn/)
>>
>>   table(3,:,:) = (/CD_bias, CD_biasn/)
>>
>>
>>
>>
>>
>>   tt_opt        = True
>>
>>   tt_opt at tableTitle  =  "Bias(%)"
>>
>>   tt_opt at pltType= "png"                  ; "eps" [default], "pdf", "ps"
>>
>>                                          ; "png", "gif" [if you have
>> ImageMajik 'convert']
>>
>> ;  tt_opt at color0 = "palegreen2"
>>
>> ;  tt_opt at color1 = "tomato2"
>>
>>   tt_opt at color0 = "white"
>>
>>   tt_opt at color1 = "white"
>>
>>
>>
>>
>>
>>   taylor_metrics_table("taylor_bias_dry", source, case ,season, table,
>> tt_opt)
>>
>>
>>
>> I have some netcdf files where the precipitation (pr) values are float
>> data type, but the _FillValue and missing_value are double. I tried convert
>> these data to float with:
>>
>>
>>
>> ncap2 -s 'pr=float(pr)' CM5A-MR_RCA4_dry_power_sm.nc
>> CM5A-MR_RCA4_dry_power_sm2.nc
>>
>>
>>
>> It converted the _FillValue to float but the missing_value are still
>> double:
>>
>> netcdf CM5A-MR_RCA4_dry_power_sm2 {
>>
>> dimensions:
>>
>>         time = UNLIMITED ; // (4 currently)
>>
>>         latitude = 201 ;
>>
>>         longitude = 464 ;
>>
>> variables:
>>
>>         float pr(time, latitude, longitude) ;
>>
>>                 pr:_FillValue = -999.f ;
>>
>>                 pr:cell_methods = "time: mean" ;
>>
>>                 pr:long_name = "precipitation" ;
>>
>>                 pr:missing_value = -999. ;
>>
>>                 pr:standard_name = "precipitation_flux" ;
>>
>>                 pr:units = "mm" ;
>>
>>         float longitude(longitude) ;
>>
>>                 longitude:standard_name = "longitude" ;
>>
>>                 longitude:long_name = "longitude" ;
>>
>>                 longitude:units = "degrees_east" ;
>>
>>                 longitude:axis = "X" ;
>>
>>         float latitude(latitude) ;
>>
>>                 latitude:standard_name = "latitude" ;
>>
>>                 latitude:long_name = "latitude" ;
>>
>>                 latitude:units = "degrees_north" ;
>>
>>                 latitude:axis = "Y" ;
>>
>>         double time(time) ;
>>
>>                 time:standard_name = "time" ;
>>
>>                 time:long_name = "time" ;
>>
>>                 time:units = "days since 1949-12-1 00:00:00" ;
>>
>>                 time:calendar = "standard" ;
>>
>>                 time:axis = "T" ;
>>
>>
>>
>> The resulted table is attached. In the table the missing values are
>> denoted by double values in CD_biasn despite the fact  that the printed
>> CD_biasn contains _FillValues:
>>
>>
>>
>> Variable: CD_biasn
>>
>> Type: float
>>
>> Total Size: 20 bytes
>>
>>             5 values
>>
>> Number of Dimensions: 1
>>
>> Dimensions and sizes:   [5]
>>
>> Coordinates:
>>
>> Number Of Attributes: 1
>>
>>   _FillValue :  -999
>>
>> (0)     -999
>>
>> (1)     -4.541727
>>
>> (2)     12.45617
>>
>> (3)     10.47692
>>
>> (4)     -999
>>
>>
>>
>> I also tried to convert the missing values to float type by ncl
>> doubletofloat function but it does not work:
>>
>>
>>
>> p8 at missing_value=doubletofloat(p8 at missing_value)
>>
>>    p8 at _FillValue = p8 at missing_value
>>
>>    delete(p8 at missing_value)
>>
>>
>>
>> fatal:Type Mismatch: The type of missing value could not be converted to
>> type of variable (p8)
>>
>>
>>
>>    p8_out = addfile("p8.nc","c")
>>
>>    p8_out ->p8 = p8
>>
>>
>>
>>
>>
>> ncdump -h p8.nc
>>
>> netcdf p8 {
>>
>> dimensions:
>>
>>         time = 4 ;
>>
>>         latitude = 201 ;
>>
>>         longitude = 464 ;
>>
>> variables:
>>
>>         float p8(time, latitude, longitude) ;
>>
>>                 p8:_FillValue = -999.f ;
>>
>>                 p8:cell_methods = "time: mean" ;
>>
>>                 p8:long_name = "precipitation" ;
>>
>>                 p8:missing_value = -999. ;
>>
>>                 p8:standard_name = "precipitation_flux" ;
>>
>>                 p8:units = "mm" ;
>>
>>         double time(time) ;
>>
>>                 time:standard_name = "time" ;
>>
>>                 time:long_name = "time" ;
>>
>>                 time:units = "days since 1949-12-1 00:00:00" ;
>>
>>                 time:calendar = "standard" ;
>>
>>                 time:axis = "T" ;
>>
>>         float latitude(latitude) ;
>>
>>                 latitude:standard_name = "latitude" ;
>>
>>                 latitude:long_name = "latitude" ;
>>
>>                 latitude:units = "degrees_north" ;
>>
>>                 latitude:axis = "Y" ;
>>
>>         float longitude(longitude) ;
>>
>>                 longitude:standard_name = "longitude" ;
>>
>>                 longitude:long_name = "longitude" ;
>>
>>                 longitude:units = "degrees_east" ;
>>
>>                 longitude:axis = "X" ;
>>
>> }
>>
>>
>>
>>
>>
>> Can someone suggest me a solution?
>>
>> Thank you for your help in advance!
>>
>> Kind regards,
>>
>> Beata
>>
>>
>>
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>
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