8.2 December 24, 2013
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Top new questions this week:
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[Any ideas on how to use the Region`
context?]\url{http://mathematica.stackexchange.com/questions/39184/any-idea
s-on-how-to-use-the-region-context}
If you type
?Region`*
you'll get:
which seems a bunch of interesting and not documented symbols.
Any idea (or experience) on how to use them?
Edit
By using our "collective spelunking" I ...
- asked by belisarius (23 votes), answered by m_goldberg (12 votes)
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[How to create effect like Van Gogh's stroke
brush?]\url{http://mathematica.stackexchange.com/questions/39003/how-to-cre
ate-effect-like-van-goghs-stroke-brush}
I need to apply Van Gogh's stroke brush effect to a random image
Take the following image as an example:
Thank you so much if you could help!
- asked by user10495 (15 votes), answered by Simon Woods (15 votes)
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[Elegant high precision
`log1p`?]\url{http://mathematica.stackexchange.com/questions/39126/elegant-
high-precision-log1p}
Sometimes it is hard to understand how numerical expressions are
evaluated. I remember reading claims by Wolfram on how smart the Kernel
is to evaluate expressions trees numerically by recognizing ...
- asked by alfC (12 votes), answered by Mark Adler (7 votes)
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[Elegantly split a matrix into positive and negative
parts?]\url{http://mathematica.stackexchange.com/questions/39113/elegantly-
split-a-matrix-into-positive-and-negative-parts}
I have a matrix $M$ of real components, and I want to split it into two
matrices $M^+$ and $M^-$ of the same dimensions as $M$, where $M^+$
contains the positive components of $M$ (the remaining ...
- asked by becko (12 votes), answered by Yves Klett (20 votes)
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[Is there a difference between Divide[a,b] and
a/b?]\url{http://mathematica.stackexchange.com/questions/39200/is-there-a-d
ifference-between-dividea-b-and-a-b}
In this comment it was asserted that Divide[a,b] and a/b are different,
though the documentation indicates that they are the same. In
particular, it was asserted that a/b is evaluated as a * 1/b, ...
- asked by Mark Adler (10 votes), answered by Szabolcs (10 votes)
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[How many Christmas
gifts?]\url{http://mathematica.stackexchange.com/questions/39338/how-many-c
hristmas-gifts}
This question is based on the old song, The Twelve Days of Christmas
In a comment made on a recent question, Yves Klett remarked, "no
seasonal questions this year?" This reminded me of one I solved ...
- asked by m_goldberg (8 votes), answered by rm -rf (13 votes)
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[Which ColorFunction should I use to get such a gradient of
blue-cyan-green-yellow-orange-red?]\url{http://mathematica.stackexchange.co
m/questions/39300/which-colorfunction-should-i-use-to-get-such-a-gradien
t-of-blue-cyan-green-yello}
I want to get the effect in the above Figure. Here is my code:
Plot3D[Log[
4*((1 + x)^2)*(0.0065^2)*Log[y]/(3*((1 - 2 x))^2*(0.0267^2)) + 1]/
Log[y], {x, 0.315, 0.45}, {y, 0, 1}, Mesh -> ...
- asked by Scott Wang (8 votes), answered by rm -rf (12 votes)
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Greatest hits from previous weeks:
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[List of compilable
functions]\url{http://mathematica.stackexchange.com/questions/1096/list-of-
compilable-functions}
Is there somewhere a list on the functions that Compile can compile, or
the cases in which a particular function can be compiled that I haven't
found?
I'd be glad even with a list of some of them ...
- asked by Rojo (58 votes), answered by Oleksandr R. (66 votes)
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[Can one identify the design patterns of
Mathematica?]\url{http://mathematica.stackexchange.com/questions/24988/can-
one-identify-the-design-patterns-of-mathematica}
... or are they unnecessary in such a high-level language?
I've been thinking about programming style, coding standards and the
like quite a bit lately, the result of my current work on a mixed ...
- asked by Verbeia (65 votes), answered by Leonid Shifrin (50 votes)
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Can you answer these?
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[Efficient submatrix swaps for large sparse
matrix]\url{http://mathematica.stackexchange.com/questions/39209/efficient-
submatrix-swaps-for-large-sparse-matrix}
I am implementing the 'swap' algorithm for a binary matrix to generate
matrix permutations that maintain row and column totals. My problem is
that my matrices are large and sparse (e.g., 19774 x 942, ...
- asked by Gareth (1 vote)
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[How to simplify
expressions]\url{http://mathematica.stackexchange.com/questions/39341/how-t
o-simplify-expressions}
I read several similar posts but I have not found a solution yet.
However, I think that my problem should be quite easy. So here we are.
Relations
Mt = M1 + M2;
x1 = -(M2/Mt)*R;
x2 = R*(1 - M2/Mt);
...
- asked by Vaggelis_Z (1 vote)
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[CountryData ->
$Failed]\url{http://mathematica.stackexchange.com/questions/39110/countryda
ta-failed}
Today I started researching the "Four colours theorem" and to do so I
need data, regions for example. I tried using the following line:
CountryData["Ukraine", "Regions"]
But the result:
...
- asked by Vitaliy Sergeyevich Barash (1 vote)