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Timeline for Linear independence of functions

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Jul 20, 2019 at 21:10 comment added mohi Thanks Anthony. I disagree that you need the points not to lie on the same plane. In particular, I think for $\phi$ that is not a polynomial and as long as $x_i=\alpha x_j$ (but $\alpha$ not necessarily positive unlike the question) the above result would hold.
Jul 20, 2019 at 21:08 comment added mohi Thanks, Pietro. I mean the latter any choice of points assumed not in "co-radial" position
Jul 20, 2019 at 8:39 comment added Anthony Quas If the $x_1,...,x_n$ lie in an affine hyperplane, you have no chance. Otherwise I would anticipate that the answer is any $\phi$ except a polynomial works. This may be morally true rather than literally true.
Jul 20, 2019 at 6:48 comment added Pietro Majer So the condition on $\phi$ refers to the given points $x_1,\dots,x_n$. Or do you mean a stronger condition, stating that the functions $\phi(w^Tx_1), \phi(w^Tx_2), \ldots, \phi(w^Tx_n)$ are linearly independent for any choice of points $x_1,\dots,x_n$ (always assumed not in "co-radial" position)?
Jul 19, 2019 at 18:49 history asked mohi CC BY-SA 4.0