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Re: Oh what is wrong with WHERE() ? [message #48568 is a reply to message #48567]

Sat, 29 April 2006 08:49

news.qwest.net
Messages: 137
Registered: September 2005

Senior Member

"Sheldon" <shejo284@gmail.com> wrote in message
news:1146322284.261031.55760@e56g2000cwe.googlegroups.com...
...
> m[nodata_tot] = 255.0
> p[nodata_tot] = 255.0
> ; finding the area with real data check
> va_data = WHERE(p EQ 255.0, COMPLEMENT=vdatap, NCOMPLEMENT=chp)
> va_data = WHERE(m EQ 255.0, COMPLEMENT=vdatam, NCOMPLEMENT=chm)
> print, 'chp: ', chp, ' chm: ', chm
...
> chp: 32271 chm: 32272
> /////////////////////////////
>
> What happened to one pixel??

Hi Sheldon,
could you reduce this problem to a very short example?
(and with m and p small enough to actually print out)?

This looks very strange in that you apparently set both m and p
to have the same number of 255s, then get different results from
the where call.. David makes a good point about the folly of
using where for equality to floats, however for this example I don't
think that causes your problem.

Offhand I would say that p already has a single value of 255 that was
not in the indexes described by nodata_tot. Thus you already had a value
for 255 before your line "p[nodata_tot] = 255.0". This line had set
1443953 points to 255, leaving 32272 points that should be other,
however on of those 32272 points in fact had a point equal to 255,
thus leaving the chp value one short at 32721.

Cheers,
bob

PS you should think hard about converting your arrays to integers
before doing any equality test.

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[Message index]

		Re: Oh what is wrong with WHERE() ? By: news.qwest.net on Mon, 01 May 2006 10:02
		Re: Oh what is wrong with WHERE() ? By: Liberum on Sat, 29 April 2006 09:15
		Re: Oh what is wrong with WHERE() ? By: news.qwest.net on Sat, 29 April 2006 08:49
		Re: Oh what is wrong with WHERE() ? By: Liberum on Sat, 29 April 2006 08:35
		Re: Oh what is wrong with WHERE() ? By: David Fanning on Sat, 29 April 2006 08:14
		Re: Oh what is wrong with WHERE() ? By: Liberum on Thu, 04 May 2006 01:18

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