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Check if coordinate is in array [message #34072]

Wed, 19 February 2003 19:34

Thomas Gutzler
Messages: 44
Registered: November 2002

Member

Hi again.

Here is the daily riddle:
Is there a faster way to check, if a coordinate (2-element array) is
element of an array of coordinates (2,n-element array) than this:

FUNCTION is_element_of_2D, x, arr
xidx = WHERE(arr[0,*] EQ x[0], c1)
yidx = WHERE(arr[1,*] EQ x[1], c2)
IF (c1 + c2 GT 0) THEN tmp = WHERE(MATRIX_MULTIPLY(xidx, $
1./TRANSPOSE(yidx)) EQ 1, c3) ELSE c3 = 0
RETURN, c3 NE 0
END

Example:
arr = [[1,2], [3,4], [3,2]]
x = [3,4]
y = [2,3]
print, is_element_of_2D(x, arr)
print, is_element_of_2D(y, arr)

Tom

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[Message index]

		Check if coordinate is in array By: Thomas Gutzler on Wed, 19 February 2003 19:34
		Re: Check if coordinate is in array By: condor on Thu, 20 February 2003 14:30
		Re: Check if coordinate is in array By: Chris[1] on Thu, 20 February 2003 06:36

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