Victor Liu
Reputation
2,416
Top tag
Next privilege 2,500 Rep.
Create tag synonyms
5 18
Impact
~18k people reached

323 Actions

 2d comment How can the centers of these 5 related circles be specified as a formula? Try the email given at the bottom of this page. 2d awarded Revival Mar24 answered Name of specific symmetric Toeplitz matrix Mar20 comment Point inside the area of two overlapped triangles There is nothing simple about this question, since there are a number of ways two triangles can overlap. The overlapping region may include none of the 6 vertices of the two triangles, so you really do need to resort to a very generic triangle-triangle intersection routine, then pick some arbitrary point in the intersecting region. Mar19 comment Silly Error calculating eigenvalues of a 3x3? Did you typo the last row of your matrix swapping $a$ and $b$?. For me, Mathematica gives the expected hand obtained results. Mar19 answered Eigenvalue of the sum of a symmetric matrix and the outer product of it's eigenvector Mar19 comment Understanding the QR eigenvalue finding algorithm @Ron Thompson: I believe so. Mar19 answered Understanding the QR eigenvalue finding algorithm Mar19 comment Understanding the QR eigenvalue finding algorithm Apologies if this is what you're doing, but I'm not sure I understand what you're saying. If the subdiagonal element $h_{j+1,j}$ has converged to zero, then the next shift should be $h_{j,j}$. Also, I stand corrected... the code does not help :) Java is so verbose... Mar19 comment Understanding the QR eigenvalue finding algorithm Can you post your test matrix and the $H$ in the iteration before it is zeroed? Also, the code would be helpful. Are you always choosing the last element of the main diagonal, or are you choosing the diagonal element above the unconverged part? Mar19 comment pseudo inverse of symmetric matrix product? @Jerry Guern: Apparently I meant "generalized reflexive inverse". You are right that the pseudoinverse is unique. The problem is that $S^{-1}M^\dagger S^{-1}SMS$ is not necessarily Hermitian since $S^{-1}M^\dagger M S^{-1}$ is not necessarily hermitian (even though $M^\dagger M$ is). Mar18 comment pseudo inverse of symmetric matrix product? The pseudo-inverse is not unique. Both forms in Mathematica give a valid pseudoinverse. Mar18 answered How to quickly determine the inverse of elementary matrices? Mar18 answered Why do I get a big relative error for my function? (Numerical Analisys - floating point) Mar14 comment Using Principal Directions and Curvatures to Find Point On Surface You only have information about the surface in the neighborhood of a $n$, so you can't be sure how the surface behaves at any finite distance away from $n$. You can assume that the surface is smooth with constant principal curvatures (so that $n$ is at the apex of a perfect ellipsoid), then the locus of points a given distance from $n$ is a sphere and you can intersect the sphere with the ellipsoid. Mar13 answered How can the centers of these 5 related circles be specified as a formula? Mar13 answered Eigenvectors of almost-Toeplitz tridiagonal matrix. Mar12 answered Area of a square inscribed in a circle Mar12 comment psuedo inverse of a matrix counter-example In that case, then the second part of my answer with the counterexample still works. Mar12 revised Given a drawing of an ellipse is there any geometric construction we can do to find it's foci? grammar