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3h
comment Deformation of pictures
See ImageTransformation and ImageForwardTransformation.
12h
comment Measuring curve length on a binarized image
I did a little Googling and this blog post is highly relevant: Measuring boundary length. It would be nice if Mathematica implemented this approach natively. You cannot even converge to $\pi$ using rasterized circles with Mathematica's current implementation :)
13h
comment Measuring curve length on a binarized image
This is probably the best built-in solution, but it's worth mentioning that it always overestimates the length of lines that are not perfectly axis-aligned or diagonal (by up to $8.2\%$).
13h
comment Measuring curve length on a binarized image
But this gives the length of the diagonal line in @halirutan's answer to be 19.
1d
comment How to generate all symmetric positive semidefinite 0,1 matrices of a given order
This question appears to be off-topic because it is about a fundamental algorithmic issue rather than about programming in Mathematica.
1d
comment region plot in a 2-simplex
It's hard to tell what you're asking. Your plot already lies in the 2-simplex $x\ge0,y\ge0,x+y\le N$. Are you looking for a plot that looks like an equilateral triangle? Please explain what you mean by "transform the region into a 2-simplex".
2d
comment Sketch-type graphics with transparency and dashed hidden lines?
@Silvia: Sweet! How did you do it?
Apr
15
comment How to work with Interpolating Function?
You should edit your question and put the code in it rather than in comments.
Apr
14
comment Getting messages Rest::norest and Divide::indet from ContourPlot3D
@Silvia, Jose: Could be an OS-dependent issue. Jose's screenshot appears to be taken on Windows, while I do get the warnings on my Mac.
Apr
13
comment Numerically Solving Compatible Systems of Overdetermined PDE
Why not just define $u(X,Y)$ by integrating $\dfrac{du}{dt} = \dfrac{\partial u}{\partial x}\dfrac{dx}{dt} + \dfrac{\partial u}{\partial y}\dfrac{dy}{dt}$ along the path $x(t) = tX$, $y(t) = tY$ for $t\in[0,1]$?
Apr
13
comment Rotational Averaging of Image Periodograms (FFTS)
I wanted to use CoordinateTransform["Polar" -> "Cartesian", #] & in the first transformation, but for some reason it didn't work. Mathematica complained that "ImageTransformation::imgtrnsfun: The function CoordinateTransform["Polar" -> "Cartesian", #1] & should map a pixel position of form {x, y} to {x', y'}", even though that's exactly what it does. What gives?
Apr
13
answered Rotational Averaging of Image Periodograms (FFTS)
Apr
13
revised Rotational Averaging of Image Periodograms (FFTS)
added 1 characters in body
Apr
13
comment Rotational Averaging of Image Periodograms (FFTS)
Not sure this is faster than the method in the question.
Apr
13
comment Why does Mathematica list the variables in a double integral backwards?
Ah, I see. Well if you read the limits first, $\int_0^a\int_0^{f(x)}$, then the iterators are in the right order. I would find it a little weird to read, say, Integrate[1, {y, 0, f[x]}, {x, 0, a}] where f[x] shows up before any mention of x.
Apr
12
comment Why does Mathematica list the variables in a double integral backwards?
I'm ashamed to admit I don't even understand the question. Integrate[x + y, {x, 0, a}, {y, 0, b}] seems fine to me. What opposite order? Can someone explain the problem to me? I'm not trying to criticise the question, I'm just curious.
Apr
11
comment Extract random points from a 3D manifold
FindInstance[1 < d < b < c && b + d < c && b + 2 d > c, {b, c, d}, Reals, 10]
Apr
11
answered Moving the location of the branch cut in Mathematica
Apr
11
comment Moving the location of the branch cut in Mathematica
Can you explain your reasoning in more detail? @Zzz's answer gives myLog[-1, 0.1] as $-2.94159i$, which is quite incorrect.
Apr
11
comment Horizontal Tree Layout?
Isn't this a duplicate of Can TreeForm be displayed “sideways”?