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A comment on Measure distance in n dimensions with Pythagoras. Parent comment

Re:Measure distance in n dimensions with Pythagoras by bluishgreen on Tuesday November 06, 2007 @10:51AM (#76613)
I think the missing element is this: you need to establish that the domain that you are trying to measure is a metric space before trying to measure distance using this formula.

http://en.wikipedia.org/wiki/Metric_space

edit: read the second section on how to establish something is a metric space. (in the wiki article)

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Re:Measure distance in n dimensions with Pythagoras by pixcavator on Tuesday November 06, 2007 @12:23PM (#76637)
Exactly! It is a big mistake to assume that you can express relations between the entities you study with a single number. I've never heard however of non-metric topological spaces used in applications.
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