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Re: NAN Problem [message #69398 is a reply to message #43584]

Wed, 13 January 2010 13:00

Foldy Lajos
Messages: 268
Registered: October 2001

Senior Member

On Wed, 13 Jan 2010, David Fanning wrote:

> Consider this sequence of commands on my IDL 7.0.1
> LINUX version.
>
> IDL> a = Findgen(11)
> IDL> a[0] = !Values.F_NAN
> IDL> Print, Min(a), Max(a)
> NaN NaN
> IDL> b = Findgen(11)
> IDL> b[1] = !Values.F_NAN
> IDL> Print, Min(b), Max(b)
> 0.00000 10.00000
>
> What do you make of that? This is giving me a great
> deal of touble today while trying to elminate bad
> values from an image. :-(
>

The first array element causes the difference. You can reproduce the
results:

min=a[0]
max=a[0]
for j=1,10 do begin
if a[j] lt min then min=a[j]
if a[j] gt max then max=a[j]
endfor

lt and gt are not defined for NaNs, they always return 0:

x=0.0
y=!Values.F_NAN
help, x lt y, x eq y, x gt y

<Expression> BYTE = 0
<Expression> BYTE = 0
<Expression> BYTE = 0

regards,
lajos

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[Message index]

		NaN problems By: David Lopez Pons on Thu, 21 April 2005 06:37
		Re: NaN problems By: R.Bauer on Sat, 23 April 2005 12:48
		Re: NaN problems By: David Fanning on Fri, 22 April 2005 20:38
		Re: NaN problems By: yp on Mon, 25 April 2005 16:51
		Re: NaN problems By: yp on Mon, 25 April 2005 16:49
		Re: NAN Problem By: R.Bauer on Thu, 14 January 2010 00:49
		Re: NAN Problem By: penteado on Wed, 13 January 2010 16:15
		Re: NAN Problem By: R.G.Stockwell on Wed, 13 January 2010 16:00
		Re: NAN Problem By: Foldy Lajos on Wed, 13 January 2010 13:00
		Re: NAN Problem By: penteado on Wed, 13 January 2010 12:59
		Re: NAN Problem By: David Fanning on Wed, 13 January 2010 12:39
		Re: NAN Problem By: jeanh on Wed, 13 January 2010 12:28

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