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Jul
2
comment MaxValue of a periodic function
BTW, regarding Interval: this works, I'm not certain if it makes sense: MaxValue[Sin[x], {x} \[Element] Interval[{-Pi, Pi}]].
Jul
2
comment MaxValue of a periodic function
Technically speaking you can have a line embedded to 1D space, but your it is still a vector variable in that space. That is, MaxValue[Sin[x], {x} \[Element] Line[{{-Pi}, {Pi}}]].
Jun
30
comment rgb2ycbcr and ycbcr2rgb performing twice on same image gives different answers?
@m_goldberg Quick googling would suggest these functions might be used in Matlab, or possibly Octave. But no, not on Mathematica...
Jun
29
comment Factoring the imaginary unit
What, exactly, you are trying to achieve? What output you are expecting to see?
Jun
29
comment How to convert a rational parametric plane curve into implicit form?
Just wondering: when will GroebnerBasis gain support for F4/F5 methods?
Jun
28
comment Optimization over 6 vectors
You can optimize over unit spheres (at least in v10): Maximize[x1 + y1^3 + x2^2 - z2, {{x1, y1, z1} \[Element] Sphere[], {x2, y2, z2} \[Element] Sphere[]}] // FullSimplify. In practice, you probably need to use NMaximize.
Jun
28
comment Does Mathematica have a built-in tool that allows one to operate on both sides of an equation?
@AlexeiBoulbitch Yes, my point was that although full forms are correct and identical to short forms, it is pretty unlikely a seasoned user would write Plus or Divide explicitly (otherwise than as a demonstration) on these cases. Maybe I'm just a bit too nit-picky... :)
Jun
27
comment Does Mathematica have a built-in tool that allows one to operate on both sides of an equation?
Frankly, I would write eq2 = Map[Expand[Divide[#, 16]] &, eq1] in practice as eq2 = Expand[#/16] & /@ eq1. Was there a specific (non-educational) point in writing Divide and Plus explicitly?
Jun
27
comment ArrayPlot of a (32767 x 125) array works but adding one row produces blank image
In this case, as you use fixed ImageSize, you would probably want to rescale your data - it only improves the visual appearance. You have to be careful to do it in linear space and perform appropriate conversions before and afterwards, though.
Jun
27
comment ArrayPlot of a (32767 x 125) array works but adding one row produces blank image
X11 (which you are using on Linux) coordinate types have maximum value of 32767. I wouldn't be surprised if something similar was in place in OSX too, although it doesn't use X11. Displaying such elements might require special-cased implementation that simply hasn't been written since there haven't been practical applications for it. You might try to compose this from multiple smaller pieces of the data aligned next to each other, though.
Jun
26
comment Is ColorDistance symmetric?
@Szabolcs Here's an example of five colors which are almost exactly at the same distance, pairwise according to CIEDE2000: i.stack.imgur.com/i4Jxy.png - it's quite clear that some of these are more separable from each other than others. It would be interesting to know if there are color distance functions also designed to make sense for large color differences, not just small ones.
Jun
25
comment Is ColorDistance symmetric?
@Szabolcs Yes. I have been experimenting with ColorDistance for quite a while, mostly to find aestetically well separable colors - and I must say result are not as neat as variance minimization algorithms would imply. Measures that would be useful on this context would be interesting to see!
Jun
24
revised Plotting 3D Intersections
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Jun
24
revised Plotting 3D Intersections
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Jun
24
comment Plotting 3D Intersections
@DavidM Have you defined variables x, y or z earlier on your session? Restarting your kernel might help.
Jun
24
revised Plotting 3D Intersections
added 11 characters in body
Jun
24
revised Plotting 3D Intersections
added 1 character in body
Jun
24
answered Plotting 3D Intersections
Jun
24
comment Is ColorDistance symmetric?
BTW, if you want to lose a bit more faith on color distance functions, please read ece.rochester.edu/~gsharma/ciede2000/ciede2000noteCRNA.pdf (The CIEDE2000 Color-Difference Formula: Implementation Notes, Supplementary Test Data, and Mathematical Observations), especially the part on discontinuities. "[...] the discontinuities do preclude the use of the formula in analysis based on Taylor series approximations and in design techniques using gradient based optimization, that not only require continuity of the function but also continuity of the first derivative."
Jun
24
comment Why doesn't ParallelTable work on this very simple example?
This is definitely an unwanted feature, as generating arbitrary-dimensional iterators and other such variables is often done with constructs like c /@ Range[dim], which is much less cumbersome than working with lists of Symbol[...], Unique[], and such.