7.19 August 26, 2014
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Top new questions this week:
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[Proving the hairy ball theorem using
xAct]\url{http://mathematica.stackexchange.com/questions/57726/proving-the-
hairy-ball-theorem-using-xact}
I would to formally prove the hairy ball theorem in Mathematica,
initially just for the $S^2$, and then see about generalizing.
An approach I thought about to use the xAct package to define $S^2$
and ...
- asked by Daniel Mahler (15 votes)
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[How to understand the usage of Inner and Outer
figuratively?]\url{http://mathematica.stackexchange.com/questions/57760/how
-to-understand-the-usage-of-inner-and-outer-figuratively}
Description:
In Mathematica the functions like Thread, Inner, Outer etc. are very
important and are used frequently.
For the function Thread:
ThreadUsage1:
Thread[f[{a, b, c}]]
{f[a], f[b], ...
- asked by Tangshutao (15 votes), answered by Timothy Wofford (5 votes)
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[Make MapIndexed
listable]\url{http://mathematica.stackexchange.com/questions/57898/make-map
indexed-listable}
My goal is to apply MapIndexed to every element of a nested list without
destroying the arithmetic operations within the elements. For example,
let's start with this list:
{a, {b, {c^d, {e + f g}}}}
...
- asked by seismatica (14 votes), answered by Mr.Wizard (10 votes)
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[Is it possible to insert new colour schemes into
ColorData?]\url{http://mathematica.stackexchange.com/questions/57885/is-it-
possible-to-insert-new-colour-schemes-into-colordata}
Because of the standards in my field, for many plots I need to use (or
at least end up using) rather narrowly defined colour schemes, and in
particular the Matlab "Jet" scheme, which is well described ...
- asked by episanty (12 votes), answered by Mr.Wizard (10 votes)
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[How to combine one or more rotated graphics
objects?]\url{http://mathematica.stackexchange.com/questions/57803/how-to-c
ombine-one-or-more-rotated-graphics-objects}
I wish to produce an image with more than one composite graphics objects
which have been modified using Rotate. I feel this should not be
difficult, but haven't yet found a solution.
A simple example ...
- asked by image_doctor (11 votes), answered by mfvonh (11 votes)
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[What is the correct way to use specific rule for specific pattern match
when parsing an
expression?]\url{http://mathematica.stackexchange.com/questions/58010/what-
is-the-correct-way-to-use-specific-rule-for-specific-pattern-match-when-
par}
update:
Thanks for the answers below. But I noticed they do not handle the
following special cases: lis=1 and lis=z , lis=1/z and lis=-z as these
are also considered legal input as given in the ...
- asked by Nasser (10 votes), answered by seismatica (6 votes)
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[Map of United States as a 3D
histogram]\url{http://mathematica.stackexchange.com/questions/57872/map-of-
united-states-as-a-3d-histogram}
By combining the state data from here and the extrusion code from here I
have managed to make prisms of the various US states such as
However, the extrusion method looses information about the ...
- asked by sonright (10 votes), answered by Vitaliy Kaurov (11 votes)
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Greatest hits from previous weeks:
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[Finding all simple paths between two vertices in a
graph]\url{http://mathematica.stackexchange.com/questions/25779/finding-all
-simple-paths-between-two-vertices-in-a-graph}
There are built-in methods to find a shortest path between two vertices
in a graph, and the question on finding all shortest paths between two
vertices has gathered quite a bit of attention.
A path ...
- asked by mrm (11 votes), answered by trybik (10 votes)
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[Marking points of intersection between two
curves]\url{http://mathematica.stackexchange.com/questions/10472/marking-po
ints-of-intersection-between-two-curves}
I'm trying to illustrate the solutions numerically and graphically for
an equation such as Tan[x] == x. I think I did everything ok except I
wanted to mark each intersection between Tan[x] and x.
...
- asked by fiz (24 votes), answered by belisarius (31 votes)
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Can you answer these?
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[Error when using
EquationTrekker]\url{http://mathematica.stackexchange.com/questions/58005/e
rror-when-using-equationtrekker}
I just got to know EquationTrakker because I need to do phase graphs for
my classes.
When I load it
<< EquationTrekker`
everything works fine with no errors.
However when I try to use an ...
- asked by Geo (2 votes)
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[How to solve for exponents in an infinite
product?]\url{http://mathematica.stackexchange.com/questions/57930/how-to-s
olve-for-exponents-in-an-infinite-product}
Say I have a power series, $f(x,y) \in 1 + x\mathbb{Z}[[x,y]]$
Then it admits a unique expansion
$$f(x,y) = \prod_{i=1}^\infty \prod_{j=0}^\infty (1 - x^i
y^j)^{n_{i,j}}$$
for some integers, $i, ...
- asked by Vivek Shende (2 votes)
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[Exporting a compiled function for later
use]\url{http://mathematica.stackexchange.com/questions/58108/exporting-a-c
ompiled-function-for-later-use}
I compiled a function then used it in NMinimize. The computation took 19
seconds. Then, I exported this compiled function and restarted MMA and
imported this compiled function into my notebook. This ...
- asked by yashar (5 votes)