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Re: How to find the pixel position [message #70672 is a reply to message #70640]

Thu, 29 April 2010 12:46

Aram Panasenco
Messages: 41
Registered: April 2010

Member

sid wrote:
> On Apr 27, 11:24 am, Aram Panasenco<panasencoa...@gmail.com> wrote:
>> sid wrote:
>>> Hi,
>>> My data is in fits format. The is of 1024 * 1024 array. The counts
>>> vary from 5000 to 6000 and I know that 5500 counts is there in my
>>> data, but I need to know at which pixel this 5500 counts occur
>>> exactly, without displaying the image, because I need to do this for
>>> several files. So each time I can't display and check for the pixel
>>> position. please helpout in this regard.
>>> regards
>>> sid
>>
>> I think what you are saying (correct me if I am wrong) is that you have
>> a 1024x1024 array, and you want to find where the pixel values are equal
>> to 5500.
>>
>> You can use the WHERE function:
>>
>> fitsData = readfits('filename.fits')
>> countValue = 5500
>>
>> findIndices = where(fitsData eq countValue)
>>
>> Note that the WHERE function returns one-dimensional subscripts. You can
>> convert them back to two-dimensional subscripts (if you need to) using
>> the ARRAY_INDICES function:
>>
>> rectIndices = array_indices([1024,1024],findIndices,/dimensions)
>>
>> Cheers
>> ~Aram Panasenco
>
> Hi,
> I did like this
> raw=readfits('filename.fits')
> b=where(raw eq 2832.90)
> I know that it occurs at raw(5,5)
> so now if I do
> print,b
> it should print 5, since where function returns one dimensional
> subscripts.(am I right, correct me if it is wrong)
> but instead it is printing -1. Please help me out.
> regards
> sid

Hey sid, other people have explained what your problem is already (can't
compare float-point values in IDL). If you want to read a more detailed
discussion on the subject, check out this article by David Fanning:

http://www.dfanning.com/code_tips/comparearray.html

~Aram Panasenco

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[Message index]

		How to find the pixel position By: sid on Mon, 26 April 2010 22:16
		Re: How to find the pixel position By: Aram Panasenco on Thu, 29 April 2010 12:46
		Re: How to find the pixel position By: sid on Thu, 29 April 2010 23:30
		Re: How to find the pixel position By: Aram Panasenco on Thu, 29 April 2010 11:42
		Re: How to find the pixel position By: jeanh on Thu, 29 April 2010 08:18
		Re: How to find the pixel position By: d.poreh on Thu, 29 April 2010 03:22
		Re: How to find the pixel position By: Timm Weitkamp on Thu, 29 April 2010 02:49
		Re: How to find the pixel position By: sid on Thu, 29 April 2010 01:50
		Re: How to find the pixel position By: d.poreh on Thu, 29 April 2010 00:06

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