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So here's an example on Wikipedia [1] https://wikimedia.org/api/rest_v1/media/math/render/svg/6c66807f5054d1175f41b90485faadfb0aaf6104 https://wikimedia.org/ap

by zmmmmm 6y ago

So here's an example on Wikipedia [1] https://wikimedia.org/api/rest_v1/media/math/render/svg/6c66807f5054d1175f41b90485faadfb0aaf6104 https://wikimedia.org/api/rest_v1/media/math/render/svg/6c66... Does the sum include both terms or only the first? I happen to know what Covariance is, but if I didn't I wouldn't be clear. I'd probably guess right, but scroll down a bit to this: https://wikimedia.org/api/rest_v1/media/math/render/svg/e6349f8dc68fcf62b45c7039e517d0ee63a1616b https://wikimedia.org/api/rest_v1/media/math/render/svg/e634... Is the +2 a multiplier on the second term or additive within the first sum? I try and read it from the spacing but I honestly can't tell. [1] https://en.wikipedia.org/wiki/Covariance https://en.wikipedia.org/wiki/Covariance

Micoloth 6y ago
I absolutely do find infuriating when math is written down vaguely/confusingly/poorly, and ML papers are a great example of this happening way too often. BUT, for your specific examples (in case that is an actual question): The first one can be parsed using the fact that y_i in the second term wouldn't make sense if it was outside the summation, since the i index is only defined inside The second (and actually, the first one, too) uses the very well established convention that multiplication always has precedence over summation, in every kind of expression. So the 2 multiplies the second sigma, and then the product is summed to the first sigma. This rule should make a lot of cases much clearer.
LudwigNagasena 6y ago
There is a reason Wikipedia is never in a syllabus in universities.