Re: logical variable fill_value

Thank you Dave and Dennis for your active support.

I have further generalized the procedure copy_VarAtts() so that it will copy
the Fill_value *only when var_to and var_from are of same datatype. *

This may be more useful than the previous version.

Please see the script.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;procedure definition
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
undef("copy_VarAtts")
procedure copy_VarAtts(var_from,var_to)
local att_names, i
begin
  att_names =getvaratts(var_from);
    if(.not.all(ismissing(att_names)))
      do i = 0,dimsizes(att_names)-1
 if ((typeof(var_to) .ne. typeof(var_from)) .and. (att_names(i) .eq.
"_FillValue")) then
     ; don't delete or assign to a logical _FillValue attribute
     continue
 else
          if (isatt(var_to,att_names(i))) then
              delete(var_to@$att_names(i)$) ; var_from att may be diff
size/type
          end if
          var_to@$att_names(i)$ = var_from@$att_names(i)$
 end if
      end do
  end if
end ;;; End of procedure copy_VarAtts();;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

It is working fine in the test run.

__________________________________

Variable: x
Type: float
Total Size: 12 bytes
            3 values
Number of Dimensions: 1
Dimensions and sizes: [3]
Coordinates:
Number Of Attributes: 2
  long_name : test_variable
  _FillValue : -999

Variable: l
Type: logical
Total Size: 12 bytes
            3 values
Number of Dimensions: 1
Dimensions and sizes: [3]
Coordinates:
Number Of Attributes: 1
  _FillValue : Missing
(0) procedure: copy_VarAtts(x,l)

Variable: l
Type: logical
Total Size: 12 bytes
            3 values
Number of Dimensions: 1
Dimensions and sizes: [3]
Coordinates:
Number Of Attributes: 2
  long_name : test_variable
  _FillValue : Missing

On 3 March 2011 12:01, gibies george <gibies@tropmet.res.in> wrote:

> Thank you Dave,
>
> I have tested *modified **copy_VarAtts procedure according to you
> suggestion. It is working fine.*
> *
> *
> *Thank you very much*
>
> Variable: x
> Type: float
> Total Size: 12 bytes
> 3 values
> Number of Dimensions: 1
> Dimensions and sizes: [3]
> Coordinates:
> Number Of Attributes: 2
> long_name : test_variable
> _FillValue : -999
>
>
> *Variable: l*
> *Type: logical*
> *Total Size: 12 bytes*
> * 3 values*
> *Number of Dimensions: 1*
> *Dimensions and sizes:** **[3]*
> *Coordinates: *
> *Number Of Attributes: 1*
> * _FillValue :** **Missing*
> *
> *
> *
> *
> *(0)** **procedure: copy_VarAtts(x,l) *
> *
> *
> *
> *
> *Variable: l*
> *Type: logical*
> *Total Size: 12 bytes*
> * 3 values*
> *Number of Dimensions: 1*
> *Dimensions and sizes:** **[3]*
> *Coordinates: *
> *Number Of Attributes: 2*
> * long_name :** **test_variable*
> * _FillValue :** **Missing*
>
> ________________________________________________________
>
> But I am getting different result in the case of normal assignment.
>
> I am using NCAR Command Language Version 5.1.1 in fedora 11
>
>
> ________________________________________________________
>
> Variable: x
> Type: float
> Total Size: 12 bytes
> 3 values
> Number of Dimensions: 1
> Dimensions and sizes: [3]
> Coordinates:
> Number Of Attributes: 2
> long_name : test_variable
> _FillValue : -999
>
>
> Variable: l
> Type: logical
> Total Size: 12 bytes
> 3 values
> Number of Dimensions: 1
> Dimensions and sizes: [3]
> Coordinates:
> Number Of Attributes: 1
> _FillValue : Missing
>
> *(0)** **normal assignment : l = x *
> *
> *
> *
> *
> *Variable: l*
> *Type: logical*
> *Total Size: 12 bytes*
> * 3 values*
> *Number of Dimensions: 1*
> *Dimensions and sizes:** **[3]*
> *Coordinates: *
> *Number Of Attributes: 2*
> * long_name :** **test_variable*
> * _FillValue :** **True*
>
>
> On 3 March 2011 01:37, David Brown <dbrown@ucar.edu> wrote:
>
>>
>> copy_VarAtts is an NCL source code procedure. It does not not have special
>> handling for the _FillValue attribute. Since the _FillValue type must agree
>> with type of the variable is belongs to, the float variable's _FillValue
>> attribute value is coerced to the logical type the same as any other value
>> would be. The rule for converting any numeric type to logical is that 0
>> converts to False and all other values convert to True. Note that during
>> normal assignment of a float variable to a logical variable this copying
>> with coercion of the _FillValue is prevented by NCL internally.
>>
>> For example:
>>
>> x = new(3,float)
>> l = new(3,logical)
>> printVarSummary(x)
>> l = x
>> printVarSummary(l)
>>
>> gives:
>>
>> Variable: x
>> Type: float
>> Total Size: 12 bytes
>> 3 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [3]
>> Coordinates:
>> Number Of Attributes: 1
>> _FillValue : 9.96921e+36
>> ncl 3> l = x
>> ncl 4> printVarSummary(l)
>>
>> Variable: l
>> Type: logical
>> Total Size: 12 bytes
>> 3 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [3]
>> Coordinates:
>> Number Of Attributes: 1
>> _FillValue : Missing
>>
>> But copy_VarAtts is a very simple procedure, and because it directly
>> assigns the attribute values itself, NCL does not, nor should it, prevent
>> the assignment. You could easily create your own version of copy_VarAtts
>> that would catch this problem and handle it. We will discuss whether we
>> should do the same.
>>
>> Here is the complete code of copy_VarAtts:
>>
>> undef("copy_VarAtts")
>> procedure copy_VarAtts(var_from,var_to)
>> local att_names, i
>> begin
>> att_names =getvaratts(var_from);
>> if(.not.all(ismissing(att_names)))
>> do i = 0,dimsizes(att_names)-1
>> if (isatt(var_to,att_names(i))) then
>> delete(var_to@$att_names(i)$) ; var_from att may be diff
>> size/type
>> end if
>> var_to@$att_names(i)$ = var_from@$att_names(i)$
>> end do
>> end if
>> end
>>
>> Perhaps (untested) add the following after do i =
>> 0,dimsizes(att_names)-1:
>>
>> if (islogical(var_to) .and. attnames(i) .eq. "_FillValue") then
>> ; don't delete or assign to a logical _FillValue attribute
>> continue
>> end if
>>
>> -dave
>>
>>
>>
>>
>> On Mar 2, 2011, at 5:38 AM, gibies george wrote:
>>
>> Here is some part of my NCL script, where I am using a user defined
>> resource variable "predef" (a logical variable with some attributes attached
>> to it) which is to be given as argument to a function to carry some
>> information about the data to be read from a source file.
>>
>> I have used copy_VarAtts function to get these attributes from a data
>> variable named "fcstdata"
>>
>> *During this operation the fill value of the logical variable is happens
>> to be "True"* .
>>
>> Why is it so ?
>> __________________________________________
>> print(predef)
>> __________________________________________
>> Variable: predef
>> Type: logical
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> Number Of Attributes: 15
>> datavar : precip
>> nosclr : 1
>> novctr : 0
>> ssnend : 9
>> ssnbegin : 6
>> season : jjas
>> loneast : 360
>> lonwest : 0
>> latnorth : 30
>> latsouth : -30
>> region : tropics
>> anal_end_year : 2001
>> anal_start_year : 1980
>> anal : skill
>> _FillValue : Missing
>> (0) True
>>
>> __________________________________________
>> delete(predef)
>> predef = new (1,logical)
>> print(predef)
>> __________________________________________
>> Variable: predef
>> Type: logical
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> Number Of Attributes: 1
>> _FillValue : Missing
>> (0) Missing
>>
>> __________________________________________
>> printVarSummary(fcstdata)
>> __________________________________________
>> Variable: fcstdata
>> Type: float
>> Total Size: 304128 bytes
>> 76032 values
>> Number of Dimensions: 4
>> Dimensions and sizes: [time | 22] x [season | 1] x [lat | 24] x [lon |
>> 144]
>> Coordinates:
>> time: [1980..2001]
>> season: [jjas..jjas]
>> lat: [-28.75..28.75]
>> lon: [1.25..358.75]
>> Number Of Attributes: 7
>> units : mm/day
>> region : tropics
>> ssnend : 9
>> ssnbegin : 6
>> long_name : jjas Means: Average Monthly Rate of Precipitation
>> season : jjas
>> _FillValue : -9.96921e+36
>>
>> __________________________________________
>> copy_VarAtts(fcstdata,predef)
>> print(predef)
>> __________________________________________
>> Variable: predef
>> Type: logical
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> Number Of Attributes: 7
>> * _FillValue :** **True*
>> * season :** **jjas*
>> * long_name :** **jjas Means: Average Monthly Rate of Precipitation*
>> * ssnbegin :** **6*
>> * ssnend :** **9*
>> * region :** **tropics*
>> * units :** **mm/day*
>> *(0)** **True*
>>
>> __________________________________________
>> predef = True print(predef)
>> __________________________________________
>> Variable: predef
>> Type: logical
>> Total Size: 4 bytes
>> 1 values
>> Number of Dimensions: 1
>> Dimensions and sizes: [1]
>> Coordinates:
>> Number Of Attributes: 7
>> _FillValue : True
>> season : jjas
>> long_name : jjas Means: Average Monthly Rate of Precipitation
>> ssnbegin : 6
>> ssnend : 9
>> region : tropics
>> units : mm/day
>> (0) True
>>
>>
>> On 2 March 2011 16:08, gibies george <gibies@tropmet.res.in> wrote:
>>
>>>
>>>
>>> On 2 March 2011 11:01, gibies george <gibies@tropmet.res.in> wrote:
>>>
>>>> Thank you Dave.
>>>>
>>>> Thanking you very much for all your supports.
>>>>
>>>> I am also thankful to Mary and Dennis for
>>>> the suggestions and support, with great patience through out the long
>>>> discussion (Both online and offline)
>>>> .
>>>>
>>>>
>>>> On 2 March 2011 06:40, David Brown <dbrown@ucar.edu> wrote:
>>>>
>>>>> Hi Gibies,
>>>>>
>>>>> There is a problem here and thank you for pointing it out. However, it
>>>>> is not what it might seem at first glance. There is one issue, admittedly
>>>>> somewhat serious: the conversion of the default logical missing value to a
>>>>> string is not working correctly. When you call 'print' with your variable
>>>>> 'full' set to the default missing value, "Missing", as follows:
>>>>>
>>>>> print("full = " + full)
>>>>>
>>>>> the value of 'full' gets converted to a string -- incorrectly, it turns
>>>>> out. However, the variable 'full' still has the correct value and the .not.
>>>>> operator is working correctly. You can see this if you print the variable
>>>>> and the expression without converting them to a string. If the first part of
>>>>> your code is changed from:
>>>>>
>>>>> print("A1 : Defineing full = new(1,logical)")
>>>>> full = new(1,logical)
>>>>>
>>>>> print("full = "+full)
>>>>> print(".not.full = "+.not.full)
>>>>>
>>>>> to
>>>>>
>>>>> print("A1 : Defining full = new(1,logical)")
>>>>> full = new(1,logical)
>>>>>
>>>>> print(full)
>>>>> print(.not.full)
>>>>>
>>>>> Instead of your output below you get:
>>>>>
>>>>> (0) A1 : Defining full = new(1,logical)
>>>>>
>>>>>
>>>>> Variable: full
>>>>> Type: logical
>>>>> Total Size: 4 bytes
>>>>> 1 values
>>>>> Number of Dimensions: 1
>>>>> Dimensions and sizes: [1]
>>>>> Coordinates:
>>>>> Number Of Attributes: 1
>>>>> _FillValue : Missing
>>>>> (0) Missing
>>>>> (0) Missing
>>>>>
>>>>> which is correct based on *the rule that any operation applied to a
>>>>> missing value yields a missing value*.
>>>>>
>>>>
>>> Actually I considered fill-value of the logical variable as a default
>>> state of a switch.
>>>
>>> I have used the not operator in that sense.
>>>
>>> I was not aware that you you were considering it as missing value same as
>>> in the case of all the other data-type.
>>>
>>>
>>>>> Setting the missing value to True, as you do in case B, inevitably
>>>>> leads to results that seem weird, even though all the results in your B
>>>>> scenario are correct by the rule above. Likewise with scenario C where the
>>>>> missing value is set to False. In most cases, although allowed, it is not
>>>>> advisable to change the missing value of logical variables from the default.
>>>>>
>>>>
>>> Isn't it possible to have such a different philosophy in the case of
>>> logical datatype.
>>>
>>> I mean an exception for logical variable alone from "*the rule that any
>>> operation applied to a missing value yields a missing value*", only for
>>> the case when fill-value is set explicitly to a value other than missing.
>>>
>>>
>>>> Case D is the same as A and has the same error. Thanks much for pointing
>>>>> this out. I'm not sure how this has managed to slip by for such a long time.
>>>>> But it will have a high priority for getting fixed quickly.
>>>>> -dave
>>>>>
>>>>>
>>>>> On Mar 1, 2011, at 9:34 AM, gibies george wrote:
>>>>>
>>>>> Here I have analysed 12 different cases of logical variable find
>>>>> its behavior to not operator.
>>>>>
>>>>> My script is attached
>>>>>
>>>>> The output is as follows.
>>>>>
>>>>> Please note the potions with red font colour.
>>>>>
>>>>> I am using NCAR Command Language Version 5.1.1 on Fedora 11 operating
>>>>> system
>>>>>
>>>>> (0) A1 : Defineing full = new(1,logical)
>>>>> *(0)** **full = True*
>>>>> *(0)** **.not.full = True*
>>>>> (0) case A2 : full = True
>>>>> (0) full = True
>>>>> (0) .not.full = False
>>>>> (0) case A3 : full = False
>>>>> (0) full = False
>>>>> (0) .not.full = True
>>>>> (0) B1 : Defineing full = new(1,logical,True)
>>>>> *(0)** **full = True*
>>>>> *(0)** **.not.full = True*
>>>>> (0) case B2 : full = True
>>>>> *(0)** **full = True*
>>>>> *(0)** **.not.full = True*
>>>>> (0) case B3 : full = False
>>>>> (0) full = False
>>>>> (0) .not.full = True
>>>>> (0) C1 : Defineing full = new(1,logical,False)
>>>>> *(0)** **full = False*
>>>>> *(0)** **.not.full = False*
>>>>> (0) case C2 : full = True
>>>>> (0) full = True
>>>>> (0) .not.full = False
>>>>> (0) case C3 : full = False
>>>>> *(0)** **full = False*
>>>>> *(0)** **.not.full = False*
>>>>> (0) D1 : Defineing full = new(1,logical)
>>>>> *(0)** **full = True*
>>>>> *(0)** **.not.full = True*
>>>>> (0) case D2 : full = True
>>>>> (0) full = True
>>>>> (0) .not.full = False
>>>>> (0) case D3 : full = False
>>>>> (0) full = False
>>>>> (0) .not.full = True
>>>>>
>>>>>
>>>>> --
>>>>> *Gibies George, CSIR-RF,
>>>>> Climate and Global Modelling Division,
>>>>> Indian Institute of Tropical Meteorology,
>>>>> Dr. Homi Bhabha Road,
>>>>> NCL (P. O.), Pashan,
>>>>> Pune 411008, India.*
>>>>>
>>>>> *http://sites.google.com/site/gibiesge/*
>>>>>
>>>>> Please Think about the environment. Save paper; Save Trees; and don't
>>>>> print this e-mail unless it is necessary.
>>>>> <trial1.ncl>_______________________________________________
>>>>> ncl-talk mailing list
>>>>> List instructions, subscriber options, unsubscribe:
>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> *Gibies George, CSIR-RF,
>>>> Climate and Global Modelling Division,
>>>> Indian Institute of Tropical Meteorology,
>>>> Dr. Homi Bhabha Road,
>>>> NCL (P. O.), Pashan,
>>>> Pune 411008, India.*
>>>>
>>>> *http://sites.google.com/site/gibiesge/*
>>>>
>>>> Please Think about the environment. Save paper; Save Trees; and don't
>>>> print this e-mail unless it is necessary.
>>>>
>>>
>>>
>>>
>>> --
>>> *Gibies George, CSIR-RF,
>>> Climate and Global Modelling Division,
>>> Indian Institute of Tropical Meteorology,
>>> Dr. Homi Bhabha Road,
>>> NCL (P. O.), Pashan,
>>> Pune 411008, India.*
>>>
>>> *http://sites.google.com/site/gibiesge/*
>>>
>>> Please Think about the environment. Save paper; Save Trees; and don't
>>> print this e-mail unless it is necessary.
>>>
>>
>>
>>
>> --
>> *Gibies George, CSIR-RF,
>> Climate and Global Modelling Division,
>> Indian Institute of Tropical Meteorology,
>> Dr. Homi Bhabha Road,
>> NCL (P. O.), Pashan,
>> Pune 411008, India.*
>>
>> *http://sites.google.com/site/gibiesge/*
>>
>> Please Think about the environment. Save paper; Save Trees; and don't
>> print this e-mail unless it is necessary.
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>>
>
>
> --
> *Gibies George, CSIR-RF,
> Climate and Global Modelling Division,
> Indian Institute of Tropical Meteorology,
> Dr. Homi Bhabha Road,
> NCL (P. O.), Pashan,
> Pune 411008, India.*
>
> *http://sites.google.com/site/gibiesge/*
>
> Please Think about the environment. Save paper; Save Trees; and don't print
> this e-mail unless it is necessary.
>

-- 
*Gibies George,   CSIR-RF,
Climate and Global Modelling Division,
Indian Institute of Tropical Meteorology,
Dr. Homi Bhabha Road,
NCL (P. O.), Pashan,
Pune 411008, India.*
*http://sites.google.com/site/gibiesge/*
Please Think about the environment. Save paper; Save Trees; and don't print
this e-mail unless it is necessary.

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