| Re: Where() with multidimensional array? [message #30182 is a reply to message #30180] |
Thu, 11 April 2002 07:31   |
Olaf Stetzer
Messages: 39
Registered: September 2001
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Member |
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David Fanning wrote:
> Olaf Stetzer (olaf.stetzer@imk.fzk.de) writes:
>
>
>> I have a problem with the where() function in IDL. It seems,
>> that the function returns -1 when confronted with a multidimensional
>> array.
>
>
> Uh, I don't think so. A -1 is returned when there is nothing
> in the array that meets the criteria. You can obtain a count
> of how may matches there are with the COUNT parameter.
Yes, it seems that all data were failvalues in my testcase.
>> I am trying the following but get an error message:
>>
>> valid=where(data ne failvalue)
>> plot.yrange[0]=min(data[valid])
>> plot.yrange[1]=max(data[valid])
> To avoid this error, I would write the code like this:
>
> valid=where(data ne failvalue, count)
> IF count GT 0 THEN BEGIN
> plot.yrange[0]=min(data[valid])
> plot.yrange[1]=max(data[valid])
> ENDIF
Thanks, this should work!
>
>> What I want is the max and min values within data (twodimensional)
>> but I want to exclude all values which are equal failvalue). Maybe there
>> is an easy way to do this?
>
>
> valid = Where( ( (data EQ Max(data)) OR (data EQ Min(data)) ) AND $
> (data NE failvalue) )
Uhmm, but that returns wrong values if failvalue is the max or min itself?
> Be aware that if you use these Boolean operators with floating point
> data that you may not get what you expect. With floats we usually
> look for values within some small delta value of the target.
In my case its exactly the value defined in failvaue. I get my data from
a mysql database and convert all NULL-values (=missing data) into a
predefined value, in this case -99999. This is in all cases below the
minimum of my data, but min(data) should return the minimum of the valid
data only!
Thanks,
Olaf
--
Dr. Olaf Stetzer
Forschungszentrum Karlsruhe
Institut fï¿œr Meterologie und Klimaforschung
Atmosphï¿œrische Aerosole (IMK III) - http://imk-aida.fzk.de
Tel.: +49(0)7247-82-3249 (FAX: -4332)
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