[ncl-talk] bias when there are missing values in one of the dataset

[Noelia otero]

Thanks for the suggestion! It worked,

Best

2017-03-13 15:02 GMT+01:00 Dennis Shea <shea at ucar.edu>:

>     v_obs = obs->tmax(:,::-1,:) ;reverse latitudes min-max
>     v_rac =racmo->tmax          ; <=== has missing values
>
> ; make both grids have the same _FillValue structure
>     vobs  = where(ismissing(v_rac), v_obs at _FillValue,  vobs)
>
>
> ===
> Hopefully, the following gives a 'global' (overall) area weighted bias
>
> ; overall (global) bias;  w are the weights: cos(rad*lat); gau(lat), ...
>
>    v_obs_mean  = wgt_areaave_Wrap(v_obs, w, 1.0, 0)
>    v_rac_mean   = wgt_areaave_Wrap(v_rac, w, 1.0, 0)
>    print(v_obs_mean)
>    print(v_rac_mean)
>
>    bias_global = v_rac - v_obs
>    bias_global at long_name = "Area weighted Bias: v_rac - v_obs"
>    bias_global at units = v_obs at units
>    copy_VarCoords(v_obs_mean, bias_global)
>    print(bias_global)
>
> ===
> An alternative is to interpolate (fill-in) all the _FillValue. However,
> you would have to proceed carefully.
>
> Good Luck
>
>
>
> On Mon, Mar 13, 2017 at 4:53 AM, Noelia otero <noeli1680 at gmail.com> wrote:
>
>> Hi!
>>
>> I am having some problems when plotting biases between two datasets in
>> those grids where one of the dataset has missing values. Here, a piece of
>> my code:
>>
>>    ;Get seasonal values for observ and mod.
>>     v_obs = obs->tmax(:,::-1,:) ;reverse latitudes min-max
>>     v_rac =racmo->tmax
>>   ; Seasonal average
>>     ;obs
>>     avgobs_seas=dim_avg_n(v_obs,0)
>>     avgobs_seas!0 = "lat"
>>     avgobs_seas!1 = "lon"
>>     avgobs_seas&lat = lat
>>     avgobs_seas&lon = lon
>>    ; model
>>     avgrac_seas =dim_avg_n(v_rac,0)
>>     copy_VarAtts(avgobs_seas,avgrac_seas)
>>     copy_VarCoords(avgobs_seas,avgrac_seas)
>>
>>    ;Bias models
>>     brac=avgrac_seas -avgobs_seas ; bias between seasonal averages
>>     copy_VarAtts(avgobs_seas,brac)
>>     copy_VarCoords(avgobs_seas, brac)
>>
>> The variable avgrac_seas contains missing values in the last latitude,
>> but not avgobs_seas.
>> So, when I compute the bias (brac), I am seeing that brac has weird
>> values for the last coordinate :
>>
>> print(brac(36,:))
>>
>> Variable: brac (subsection)
>> Type: double
>> Total Size: 384 bytes
>>             48 values
>> Number of Dimensions: 1
>> Dimensions and sizes:   [48]
>> Coordinates:
>> Number Of Attributes: 1
>>   _FillValue :  -32767
>> (0)     -10271.61482711738
>> (1)     -10271.85755532229
>> (2)     -10272.11799386223
>> (3)     -10272.37392089582
>> .......................................................
>>
>> and finally , my plot looks wrong ...
>> Any suggestion to solve this? Should I filter the missing values before?
>>
>> Many thanks in advance,
>>
>> Noelia
>>
>>
>>
>>
>>
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170314/53dff2b6/attachment.html