================================== Top new questions this week: ==================================
[Why is calling Dot with many arguments so inefficient?] http://mathematica.stackexchange.com/questions/83412/why-is-calling-dot-with-many-arguments-so-inefficient
Say I want to multiply a reasonably large list of symbolic matrices.
tab = Partition[#,4]&/@ Table[ Symbol[CharacterRange["a","z"][[nm]]<>ToString[nn]],{nn,1,12},{nm,1,16}];
...
- asked by murphy (13 votes), answered by Hurkyl (7 votes)
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[Performance problems in new Sequence functions]http://mathematica.stackexchange.com/questions/83325/performance-problems-in-new-sequence-functions
The new-in-10.1 Sequence* family of functions should provide newly optimized methods for handling sequence problems. Happily in some cases they do! For example Murta reports 28 times faster ...
- asked by Mr.Wizard (12 votes)
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[What are SparseArray Properties? How and when should they be used?]http://mathematica.stackexchange.com/questions/83721/what-are-sparsearray-properties-how-and-when-should-they-be-used
A strange undocumented form of SparseArray is increasingly used in answers on this site:
SparseArray[(* data *)]["NonzeroPositions"]
What is this, and why would anyone want to use this? Are there ...
- asked by Mr.Wizard (11 votes), answered by Mr.Wizard (12 votes)
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[A better (but slower) FullSimplify function]http://mathematica.stackexchange.com/questions/83756/a-better-but-slower-fullsimplify-function
I am creating this question and posting an answer to it as a help for those who have problems with Mathematica simplification oddities that appear in many other questions on the site.
First of all, ...
- asked by Giovanni (10 votes), answered by Giovanni (10 votes)
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[Is there a programmatic equivalent of Edit > Find?]http://mathematica.stackexchange.com/questions/83492/is-there-a-programmatic-equivalent-of-edit-find
Most things that can be done via the front-end interface in Mathematica can also be accomplished by some function. Is that the case for find-and-replacing? That is, is there some code I could execute ...
- asked by thecommexokid (10 votes), answered by Mr.Wizard (10 votes)
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[Is FullGraphics an abandoned function? Is there an alternative?]http://mathematica.stackexchange.com/questions/83648/is-fullgraphics-an-abandoned-function-is-there-an-alternative
FullGraphics hasn’t worked entirely for a long time and the situation appears to be getting worse instead of better. In Mathematica 10.0 and 10.1 a simple usage throws numerous errors and returns a ...
- asked by Mr.Wizard (10 votes)
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[How to find all the positions of max value of a list efficiently?]http://mathematica.stackexchange.com/questions/83602/how-to-find-all-the-positions-of-max-value-of-a-list-efficiently
For Example, list=RandomInteger[1,100,2000]. Yes,I know Position[list,Max[list]] can do. But it’s based on pattern matching! Ordering[list,-1] could find one position but not all. So how to ...
- asked by WateSoyan (10 votes), answered by Pickett (14 votes)
================================== Greatest hits from previous weeks: ==================================
[How to make use of Associations?]http://mathematica.stackexchange.com/questions/52393/how-to-make-use-of-associations
I have been curious about it for long. Now that Mathematica 10 arrives, I think it’s time to ask the question: How the new Association data structure would be used to improve Mathematica programming?
...
- asked by Yi Wang (74 votes), answered by Leonid Shifrin (80 votes)
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[How to find the position of elements in a list satisfying criteria] http://mathematica.stackexchange.com/questions/180/how-to-find-the-position-of-elements-in-a-list-satisfying-criteria
Say I have a list x=2,4,6,8,10 and I want to find out the positions of the elements that are greater than 7.
Select[x, #>7&] gives the elements themselves, and Position[x,8] gives the ...
- asked by PeterR (24 votes), answered by Guess who it is. (19 votes)
================================== Can you answer these? ==================================
[Indeterminate expression 0(I*Infinity]) on indefinite integrals on first use only]http://mathematica.stackexchange.com/questions/83450/indeterminate-expression-0iinfinity-on-indefinite-integrals-on-first-use-onl
I do not know if this is new or not, I googled before.
Windows 7, 10.1 64 bit: Integrals generate this error message
The strange thing also is that the message shows up the first time the command ...
- asked by Nasser (3 votes)
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[Undo automatic update] http://mathematica.stackexchange.com/questions/83795/undo-automatic-update
I was working with Predict function (with a neural network and today, and when I executed the same notebook I have been working for some time, Machine Learning package was automatically updated (it ...
- asked by Miguel (2 votes)
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[How to match the arguments of the function in any order] http://mathematica.stackexchange.com/questions/83396/how-to-match-the-arguments-of-the-function-in-any-order
The issue is the following, with a dumb function with (4) arguments of (4) different heads (for each head is always no grater than one arguments):
func[x_a,y_b,z_c,w_d] := Print[x,y,z,w]
If I type ...
- asked by d555 (3 votes)