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Re: Setting values to NaN [message #39928 is a reply to message #39927]

Fri, 25 June 2004 08:50

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Matt wrote:
> OK I spotted it. F_NAN and D_NAN apply to floats.
>
> So is there an alternative I can use with integers?

How would you define a bit pattern for an invalid integer that's not a valid integer?, as
opposed to some user-set value (like -99 or or -32767 or -2147483647L etc.) ?

You need to define some user-set value (like -99 or or -32767 or -2147483647L etc.) based
on what you knwo about your data. Something like:

IDL> MY_INVALID_INTEGER = -32767
IDL> a = indgen(10)
IDL> lt5 = where(a lt 5)
IDL> a[lt5] = MY_INVALID_INTEGER
IDL> print, a
-32767 -32767 -32767 -32767 -32767 5 6 7 8 9

Be careful about mixing values/data types though:

IDL> MY_INVALID_INTEGER = -2147483647L
IDL> a = indgen(10)
IDL> lt5 = where(a lt 5)
IDL> a[lt5] = MY_INVALID_INTEGER
IDL> print, a
1 1 1 1 1 5 6 7 8 9

paulv

>
>
> matt_westmore@yahoo.co.uk (Matt) wrote in message news:<c66373b9.0406250228.f6cbaf4@posting.google.com>...
>
>> Hi,
>> I'd realy appreciate someone pointing out why I'm an idiot.
>>
>> I'm trying to set some values of an image to NaN so that they are not
>> included in further calculations but I can't seem to do it!!!
>>
>> eg:
>> a = indgen(10)
>> lt5 = where(a LT 5)
>> a(lt5) = !VALUES.F_NAN
>> %Program caused arithmetic error: Floating illegal operand
>> print, a
>> 0 0 0 0 0 5 6 7 8 9
>>
>> Cheers
>> Matt

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[Message index]

		Re: Setting values to NaN By: Craig Markwardt on Fri, 25 June 2004 13:17
		Re: Setting values to NaN By: b_gom on Fri, 25 June 2004 11:38
		Re: Setting values to NaN By: Matt Feinstein on Fri, 25 June 2004 09:34
		Re: Setting values to NaN By: Michael Wallace on Fri, 25 June 2004 09:30
		Re: Setting values to NaN By: Craig Markwardt on Fri, 25 June 2004 09:14
		Re: Setting values to NaN By: Paul Van Delst[1] on Fri, 25 June 2004 08:50
		Re: Setting values to NaN By: matt_westmore on Fri, 25 June 2004 08:27
		Re: Setting values to NaN By: David Fanning on Fri, 25 June 2004 06:43
		Re: Setting values to NaN By: Klaus Scipal on Fri, 25 June 2004 04:41
		Re: Setting values to NaN By: matt_westmore on Wed, 30 June 2004 04:37

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