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jeanluct / braidlab

Matlab package for analyzing data using braids
GNU General Public License v3.0
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Zero-index in a braid. #60

Closed jeanluct closed 9 years ago

jeanluct commented 9 years ago

Should zero-index be allowed in a braid? It looks like it is a place-holder for the identity element to me, (braid([],3) == braid(0,3) for example), but if you run plot(braid(0,3) a non-trivial braid is plotted.

jeanluct commented 9 years ago

From Jean-Luc Thiffeault on 2014-09-18 15:30:53+00:00

Good question... if we do allow it, then we have to make sure that compact([1 0 -2]) returns [1 -2]. I'm not sure we should allow it... It would at the very least require a lot of testing to make sure nothing breaks.

But you're right that if we do disallow it, then we should forbid braid(0,3).

jeanluct commented 9 years ago

From Marko Budisic on 2014-09-18 15:51:57+00:00

My vote would be to disallow it... the only reason for allowing it, in my mind, would be for data braids, where you'd want to mark, for some reason, a time at which no exchanges happen. Zeros would then be a way of making sure that the time vector and generator vector match. But at this point, I don't foresee this being useful in our context.

jeanluct commented 9 years ago

From Jean-Luc Thiffeault on 2014-09-21 22:24:48+00:00

Check for zero generators in braid.set.word, and add unit test. Resolves issue #60.

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