Talk:Support vector machine/Archives/2017

Wrong formula for regression (?)

The formula reported for regression appears to be wrong (to me) in the "subject to" part. In particular, the left-hand sides are the same except the signs (the first one is the opposite of the second one). As it is it does not make sense. — Preceding unsigned comment added by 93.148.3.203 (talk) 10:52, 27 April 2017 (UTC)

I agree that it looks wrong—it looks like the absolute value of the expression ought to be no greater than epsilon. But reference [73], in its expression (2), writes it in the same odd way. Loraof (talk) 22:06, 17 August 2017 (UTC)

Actually the two constraints do have the effect of saying that the absolute value of the expression must be no greater than epsilon. With simplified notation the constraints say $z\leq \epsilon$ and $-z\leq \epsilon .$ If z≥0, the first constraint says z must be no greater than epsilon in absolute value, while the second constraint says that a negative must be no greater than a positive, which is nonbinding. And if z<0, the second constraint says that the absolute value of z must be no greater than epsilon, while the first constraint says nonbindingly that a negative must be no greater than a positive. So the combined effect is that $|z|\leq \epsilon .$ Expressing it in absolute value form is more intuitive and readily readable, but expressing it as the article does is how you actually give the instruction to some regression packages. Loraof (talk) 03:51, 18 August 2017 (UTC)