Rahul
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 Dec 25 answered Prevent Plus from threading Dec 25 comment Prevent Plus from threading Thanks for all the answers, everyone! I guess I should have been more forthcoming about my ultimate goal, namely getting a correct PiecewiseExpand[f[t, 0, 2]] for my Koch snowflake parametrization, because I couldn't figure out make the answers here work for it. But seeing all the different approaches inspired a solution of my own that did work out (though still not as elegant as I would like). Dec 24 asked Prevent Plus from threading Dec 24 answered Revolution of Koch Snowflake Dec 23 comment Eigenvectors choose intuitive ordering/sorting But you said you want the eigenvectors of a diagonal matrix to form the identity matrix. Dec 23 comment Eigenvectors choose intuitive ordering/sorting In general what you are asking for is not possible. For example, the eigenvectors for $\begin{bmatrix}1&\epsilon\\\epsilon&1\end{bmatrix}$ are $(1,1)^T$ and $(1,-1)^T$ for any $\epsilon>0$, so there is no way for the eigenvector matrix to approach the identity as $\epsilon\to0$. You may have to write your own eigenvalue algorithm for your specific problem. Dec 22 comment polar form of generalized superellipse (not Gielis formula!) Well, why don't you just fix $m=4$ in the Gielis formula to get the usual fourfold symmetry? Dec 21 comment Creating curves that satisfy $f(x)\le g(x)\le h(x)$ "Exactly" like it? It sure looks to me like it was drawn by hand (in an illustration program). Dec 20 comment Randomly generate points on a van der Waals surface For example, set s = DiscretizeRegion[ImplicitRegion[Min[EuclideanDistance[{x, y, z}, #] & /@ carbonXYZ] == rc + ra, {x, y, z}], {{-1, 28}, {-2, 23}, {-5, 5}}, MaxCellMeasure -> 0.1] and then RandomPoint[s] is extremely fast. Dec 20 comment Randomly generate points on a van der Waals surface Aren't you already aware of RandomPoint? Dec 19 revised Convert large KML coordinate datasets to UTM edited tags Dec 19 comment Convert large KML coordinate datasets to UTM Dec 19 comment How to solve partial differential equation There is no a or b in your code, so presumably you have some leftover variable definitions. Try clearing them. Dec 18 comment How to find a starting value that is closer to the solution? Wouldn't it be easier to (i) solve the first equation for $x$, (ii) solve the second equation for $y$, and then (iii) set $R = c/(y-x)$? Dec 18 comment Plot region from given coordinates Yes, that's fine, but why is that a problem? You say this approach "does not work", but the asker didn't ask for a convex figure. Dec 18 comment Plot region from given coordinates Why is it a problem if the FindShortestTour solution is not convex? Dec 17 awarded Revival Dec 17 answered Limits explanation in doc Dec 17 comment Plot region from given coordinates Dec 15 comment Interpreting the result of ContourPlot3D Fundamentally this is because the ContourPlot* functions rely on the intermediate value theorem, which breaks down here because the function is not continuous.