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Re: FINITE function [message #90050 is a reply to message #90049]

Wed, 21 January 2015 04:14

andeh
Messages: 23
Registered: April 2011

Junior Member

On Wednesday, 21 January 2015 12:00:29 UTC, g.na...@gmail.com wrote:
> Hi I used the FINITE() function as suggested to find out whether there are nans or infinity numbers in my array. The problem is that I cannot understand the output of that function. I set the keyword SIGN = 1 but I got -1 inthe outcome.
>
> Below is a part of the code:
>
> DataArray ; contains the 3D data
>
> for i = 0, 199 do begin
> for j = 0, 199 do begin
> Barray = DataArray[*,i,j] - Array[i,j]
> print, where(finite(Barray), /INFINITY, SIGN=1))
> endfor
> endfor
>
> I got the -1 value thousands of times maybe and I am not even able to figure out in which place of that array there are infinity or nans (if there are any)
>
> Can anyone help with this?

Your test is only looking for positive infinity so all finite numbers, negative infinities, and NaNs will not be flagged. e.g.

IDL> PRINT, FINITE( 1.0, /INFINITY, SIGN=1), WHERE(FINITE( 1.0, /INFINITY, SIGN=1))

IDL> PRINT, FINITE( !VALUES.F_NAN , /INFINITY, SIGN=1), WHERE(FINITE( !VALUES.F_NAN , /INFINITY, SIGN=1))
0 -1

IDL> PRINT, FINITE( -!VALUES.F_NAN , /INFINITY, SIGN=1), WHERE(FINITE( -!VALUES.F_NAN , /INFINITY, SIGN=1))
0 -1

IDL> PRINT, FINITE( 1.0 / 0.0 , /INFINITY, SIGN=1), WHERE(FINITE( 1.0 / 0.0, /INFINITY, SIGN=1))
1 0

IDL> PRINT, FINITE( -1.0 / 0.0 , /INFINITY, SIGN=1), WHERE(FINITE( -1.0 / 0.0, /INFINITY, SIGN=1))
0 -1

You are getting -1 values from WHERE(). This means that there are no matching elements in FINITE(Barray).

To search for all non-finite numbers, make your search
WHERE( ~FINITE(Barray) )

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[Message index]

		FINITE function By: g.nacarts on Wed, 21 January 2015 04:00
		Re: FINITE function By: andeh on Wed, 21 January 2015 04:14
		Re: FINITE function By: andeh on Wed, 21 January 2015 04:20
		Re: FINITE function By: g.nacarts on Wed, 21 January 2015 05:35
		Re: FINITE function By: andeh on Wed, 21 January 2015 05:49
		Re: FINITE function By: andeh on Wed, 21 January 2015 05:52
		Re: FINITE function By: andeh on Wed, 21 January 2015 05:53
		Re: FINITE function By: g.nacarts on Wed, 21 January 2015 07:22

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