# Rahul Narain

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 Mar26 comment Solving a system of 4 logarithmic equations? I'm just curious why you posted an answer that finds a non-solution eight hours after RiemannZeta already proved that there are no solutions. Mar26 comment Solving a system of 4 logarithmic equations? I get a warning, FindRoot::cvmit: Failed to converge to the requested accuracy or precision within 100 iterations. And substituting the values into the equations gives $11.5863 = 20$, $6.32768 = 125$, $4.74367 = 710$, $4.49181 = 1350$. Mar24 comment Area of a convex polygon with a set of points If your polygon is known to be convex then ordering by angle relative to the mean of the vertices will also work. Mar22 comment Eigenvector Anomaly @rm-rf: Done. I hope Peter doesn't mind. Mar22 revised Eigenvector Anomaly changed to a question about Mathematica Mar22 comment Eigenvector Anomaly If we edited the question to replace the W|A queries with Mathematica commands, the difference would remain and the question would be on-topic. But is that too radical a change from the original question? Mar21 comment Choosing $n$ equidistant points on a circle with given radius and center @Pavithran Your code creates $n+1$ points of which the first and last are the same. I'm not sure that's what you want. Mar19 comment Plot 3D density Have you tried ListContourPlot3D? By the way, your title is misleading: this is a 3D density, that is, a density over a three-dimensional region. Mar18 comment How can I define a 3d-body through different views? Here's a smooth plot of what I think is the same object: ContourPlot3D[x^2 + (y/(1 - z))^2 == 1, {x, -1, 1}, {y, -1, 1}, {z, 0, 1}, BoxRatios -> Automatic] i.stack.imgur.com/CIqpO.png Mar17 comment Find the eigenvector associated with the smallest eigenvalue, not smallest in magnitude I would have suggested finding the eigenvectors of $I + \epsilon A$ for sufficiently small $\epsilon$, but since you don't have a lower bound for the smallest eigenvalue you can't be sure that $\epsilon$ is sufficiently small. And in any case this might amplify the numerical error you incur. Mar12 comment What type of solver does Mathematica use in LinearSolve How on earth can any solver fail on a diagonal matrix? Mar8 comment How do I NOT change the input/output number when editing? Yes, this does sound like a case of "Doctor, doctor, it hurts when I do this." "So don't do that then." Mar7 comment 2D Fourier transform of a table - ArrayPlot issue I guess what you're looking for is an analogue of Matlab's fftshift. It's not really an issue with ArrayPlot, it's an question of visualizing the result of the Fourier transform. Mar5 comment Colorize a 3D distribution of points according to density Unfortunately SmoothKernelDistribution is new in 8.0. Mar4 comment How to obtain differential equations of motion using Lagrangian dynamics? @Nasser: "You do not really count the unstretched length of the spring is L in these problems, since one always starts from the relaxed position. The initial stretched length of the spring is already account for." This is quite incorrect. Only if the problem is one-dimensional, and one end of the spring is fixed, and you choose the origin of the coordinate system at the relaxed position of the other end, then your statement is valid. This is not the case for this problem. Mar4 comment Variance/Standard Deviation with a Constant Vaule For one thing, Variance expects a list, so you'd need to do Variance[{10}] instead. But for another thing, Variance returns the sample variance, with $n-1$ in the denominator, so the variance of a sample of length $n=1$ is not defined at all. Mar3 comment Manipulating infinite series Don't you want -Sum[f[x], {x, m, m+2}] instead? Mar1 revised StreamPlot for Bifurcation Diagram added 521 characters in body Mar1 answered StreamPlot for Bifurcation Diagram Feb28 comment Finding the optimal teams ranking based on the table of match results Are you absolutely sure you want to iterate over all 90 billion permutations? That's a lot of iterations. If I were you, I'd first ask on math.stackexchange.com whether there exists a more efficient algorithm that doesn't take superexponential time, and then implement that instead.