| Re: Missing Data Programming Contest [message #65994 is a reply to message #65993] |
Wed, 08 April 2009 16:26   |
Homeyer
Messages: 9
Registered: March 2009
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Junior Member |
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On Apr 8, 6:02 pm, Homeyer <cam.the.weather....@gmail.com> wrote:
> On Apr 8, 8:23 am, David Fanning <n...@dfanning.com> wrote:
>
>
>
>> Folks,
>
>> I don't have time today to think about this, so I've
>> decided to get you to do my thinking for me. :-)
>
>> Suppose you are expecting a data array and you suspect
>> the data has "missing values" in it that you wish to
>> exclude from further processing. You write a keyword
>> for your routine that allows the user to pass in what
>> he is using for the "missing value".
>
>> PRO Junker, data, MISSING_VALUE=missing_value
>
>> How would you write the code to assure that this missing
>> value would be excluded from further processing?
>
>> You should assume:
>
>> 1. The data can be any data type except complex or string.
>
>> 2. The missing value *could* be !VALUES.F_NAN.
>
>> 3. Unsophisticated users might be using your program,
>> so, for example, they might pass in a missing value
>> such as 594.32.
>
>> No, this is NOT my homework! But I do need it ASAP. ;-)
>
>> Cheers,
>
>> David
>> --
>> David Fanning, Ph.D.
>> Fanning Software Consulting, Inc.
>> Coyote's Guide to IDL Programming:http://www.dfanning.com/
>> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
>
> The following should suffice:
>
> IF (missing_value GT 0) THEN BEGIN
> type = SIZE(array, /TNAME)
>
> CASE type OF
> 'COMPLEX' : MESSAGE, 'Complex values not allowed for removing
> MISSING data.'
> 'STRING' : MESSAGE, 'String values not allowed for removing
> MISSING data.'
> ELSE : invalid = WHERE((array EQ missing_value), iv_count,
> COMPLEMENT = valid, NCOMPLEMENT = v_count)
> ENDCASE
>
> IF (v_count GT 0) THEN array = array[valid]
> ENDIF
>
> That is, if you dont care about overwriting the original data or it is
> not gridded. If it is gridded (data points with missing values should
> remain), then you could replace those with NaNs in the final array
> using the indices above.
>
> Cheers,
> Cameron Homeyer
oops, missed the NaN part:
This would go before the last IF (v_count...
IF (~FINITE(missing)) THEN invalid = WHERE(~FINITE(array), iv_count,
COMPLEMENT = valid, NCOMPLEMENT = v_count)
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