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Re: How to find second minimum and maximum in 3D array? [message #90357 is a reply to message #90355] Wed, 25 February 2015 13:31 Go to previous message
Harald Frey is currently offline  Harald Frey
Messages: 41
Registered: March 1997
Member
On Wednesday, February 25, 2015 at 1:25:44 PM UTC-8, Craig Markwardt wrote:
> On Wednesday, February 25, 2015 at 3:01:53 PM UTC-5, hf...@ssl.berkeley.edu wrote:
>> I have a time series of ~200 images with dimensions [X,Y]=[400,250]. My data is a UINTARR[200,400,250]. It is very easy to get the minimum and maximum for each pixel X,Y in my time series using
>>
>> res=min(array,dimension=1,max=max_val)
>> IDL> help,res,max_val
>> RES FLOAT = Array[400, 250]
>> MAX_VAL FLOAT = Array[400, 250]
>>
>> However, several pixels have 0 value or 65535 value and I want the second minimum and second maximum which are not 0 or 65535. I can do this in a for-loop, but is there a more clever and faster way?
>
> You could use WHERE() once to find the pixels that are 0 or 65535, and then set those to NAN. Then you can use min() or max() directly with the /NAN keyword to ignore NAN values.
>
> Craig

Perfect! That should really speed thing up.
Thanks a lot!
Harald

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