32,955 reputation
878162
bio website
location
age
visits member for 2 years, 7 months
seen Jun 24 '13 at 0:02

No, his mind is not for rent
to any god or government.
Always hopeful, yet discontent.
He knows changes aren't permanent,
but change is.

— Rush, Tom Sawyer


Taking an externally-imposed and much-needed break from SE activities.

E-mail (flipped ROT13): zqd˙ʎʌuzʇ@ʇɐʌǝɥʇʌssqɹǝɥɟuɹʎɔ
Any code I've posted here I place under the WTFPL.


Sep
9
revised Ordering problem
deleted 4 characters in body; edited tags
Sep
9
comment How do I find an equilateral triangle whose vertices have integer coordinates?
See this math.SE question. As noted there, in 3D, you can have an equilateral triangle with integer coordinates (it is easy to construct an octahedron with integer coordinates, and its faces are equilateral triangles); in 2D, this is impossible.
Sep
9
revised How do I find an equilateral triangle whose vertices have integer coordinates?
edited tags
Sep
9
revised How can I solve the equation with integers as a solution?
deleted 1 characters in body
Sep
9
revised On generalizing Partition[] (with offsets) to sublists of unequal length
slight generalization
Sep
9
reviewed Edit suggested edit on First evaluation fails
Sep
9
revised First evaluation fails
added 13 characters in body
Sep
9
revised How to add a short wav music clip into a Mathematica animation
edited tags
Sep
9
revised How to Solve or LinearSolve $A = I$ matrix equation?
edited tags
Sep
8
revised Trying to calculate a sum within a module - why is the iterator not creating integers?
edited tags
Sep
8
revised matrix wiki description
deleted 8 characters in body
Sep
8
revised matrix wiki excerpt
edited body
Sep
8
comment Mathematica for linear algebra course?
Could you mention the textbook you're using?
Sep
7
comment How to check if a 3D point is in a planar polygon?
I'd do First[SingularValueDecomposition[vertices - Mean /@ vertices, 2]] myself... but wait, shouldn't that be # - Mean[vertices] & /@ vertices (i.e., Standardize[vertices, Mean, 1 &])?
Sep
7
comment How to check if a 3D point is in a planar polygon?
Hah, nice! I forgot that PCA can do the job here, even though it is not the most efficient way to go about things... but safe nevertheless.
Sep
7
comment How to check if a 3D point is in a planar polygon?
One way to safen the implementation of basis[] would be to take the Mean[] of the polygon's points and use that as the x... on another note, for your inPlane[], might it be better to do the test as Chop[Det[(* stuff *)]] == 0?
Sep
7
revised How to check if a 3D point is in a planar polygon?
deleted 4 characters in body
Sep
7
comment How to check if a 3D point is in a planar polygon?
@Eli: equation 18 here might give you a clue on how to do the checking. (I used it in the coplanarQ[] function I mentioned in another comment.)
Sep
7
comment How to check if a 3D point is in a planar polygon?
I prepared for the possibility that the first and last entries in the point list being the same, among other things. I use Chop[stuff] == 0 as the test, in the event that (angle sum) - 2 π is a tiny nonzero number that should be zero, but isn't.
Sep
7
comment How to check if a 3D point is in a planar polygon?
@Simon, for polygons with inexact coordinates, it'd be safer to use Newell's algorithm to compute the normal...