| Re: Missing Data Programming Contest [message #65995 is a reply to message #65994] |
Wed, 08 April 2009 16:02   |
Homeyer
Messages: 9
Registered: March 2009
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Junior Member |
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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
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