Reputation
20,434
Next privilege 25,000 Rep.
Access to site analytics
Badges
2 48 94
Newest
 Nice Answer
Impact
~206k people reached

Mar
23
comment How can I optimize the search between two lists, one that is changing length?
If you really want to find out about n=6, get a book like "Hackers Delight", translate the transpose/reverse operations to bit-twiddling operations, and learn C. Back-of-the envelope calculation suggests that it should be possible to run this for n=6 in hours. But that it something you'd have to do yourself ;-)
Mar
23
comment How to define a set of two random orthogonal unit vectors?
n[k_]:= defines a function of k. If you call it 3 times with the same argument, it gets evaluated 3 times and you get 3 different random vectors
Mar
23
comment How can I optimize the search between two lists, one that is changing length?
If you're going to use Association, you should probably read the documentation and tutorials in MMA. Anything else will only lead to frustration. That said, you probably want Export[... Keys[uniqueArray] ...]
Mar
23
comment How can I optimize the search between two lists, one that is changing length?
Try this: open a new notebook, restart the kernel, copy&paste your code from the start up to (and including) m[1]; // AbsoluteTiming and run. I get a lot of warnings then, apparently on the second call to m. Maybe some cleanup is missing from m
Mar
22
answered How can I optimize the search between two lists, one that is changing length?
Mar
22
comment How can I optimize the search between two lists, one that is changing length?
FWIW, I'd try to replace AppendTo with an Association, which should make insertion faster
Mar
22
comment How can I optimize the search between two lists, one that is changing length?
How large would you like n to get? Even if you'd optimize the Table calculation to do one iteration per nanosecond, n=8 would take over 500 years. 2^n^2 simply grows very fast. Unless you come up with a different algorithm, anything above n=5 or maybe n=6 will take a very long time.
Mar
18
comment How to Flatten and stack Efficiently 50000 Images
Like I said, you can avoid the memory cost, but there's not much you can do to improve Import's speed without rewriting the functionality.
Mar
18
answered How to Flatten and stack Efficiently 50000 Images
Mar
18
awarded  Enlightened
Mar
18
comment ImageData reverses the order of the row of an Image
But indices still start at 1, coordinates at 0. Plus, rotating the whole image just to get one pixel is horribly inefficient. I'd prefer with GetPixelValue...
Mar
18
awarded  Nice Answer
Mar
18
revised ImageData reverses the order of the row of an Image
added 998 characters in body
Mar
18
comment Total and partial derivatives
Maybe what you want is: ff = f[x, y]; Dt[ff, x] - (D[ff, x] + D[ff, y] Dt[y, x])
Mar
18
comment Total and partial derivatives
D is applying the chain rule. What else would you expect? If y were e.g. Sqrt or Sin, would you expect D[f[x, Sin[x]], x] == f'[x, Sin[x]]?
Mar
18
answered ImageData reverses the order of the row of an Image
Mar
14
comment Measure perimeter of black edge in Mathematica
@yode: I think it's because you use Dilation[..., 1], which uses BoxMatrix[1] as structuring element - meaning, you're using an 8-neighborhood, where I use a 4-neighborhood
Mar
14
awarded  Enlightened
Mar
14
awarded  Nice Answer
Mar
14
awarded  image-processing