is there any way to check if any point exactly overlaps with another point?

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Charles David 2013-2-15

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https://ww2.mathworks.cn/matlabcentral/answers/63558-is-there-any-way-to-check-if-any-point-exactly-overlaps-with-another-point

I basically have data in many files.i.e latitude longitude and temperature. Now when a new file comes in i want to be able to check if any record has the same latitude and longitude combination and if it does i want to ignore it.I know it can be done through a program but i think it will take a very long time to check this for every particular record and may take around O(n^2).Is there any other way to do this???

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Answer 1

Walter Roberson 2013-2-15

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How are the latitude and longitude represented? If they are floating point numbers, then you will have a problem. See http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

If you use a binary search, then you can determine match or not in log2(n) time, and so can do all of the checks in at most O(n*log(n)) time. O(log(n!)) time really. Excluding the cost of the insertions (which would be at the point the match was determined not to exist.)