15 votes
Accepted

Association vs Pair - Creation performance, Selection performance

Simply use keys = Range[1000000]; vals = Range[1000000]^2; result = Pick[vals, PrimeQ[keys]]; to get the best of both worlds (zero construction cost and even ...
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11 votes
Accepted

How can I use variables instead of slots in DeleteCases?

...
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11 votes

How can I use variables instead of slots in DeleteCases?

Pick could also be useful: Pick[tuples, Function[{a, b, c}, a + 2 b + c == 0] @@@ tuples, False]
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  • 5,089
8 votes

How can I use variables instead of slots in DeleteCases?

g[{a_, b_, c_}] := a + 2 b + c == 0 Using the operator form: DeleteCases[x_ /; g[x]][tuples]
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8 votes

How can I use variables instead of slots in DeleteCases?

Perhaps (Thanks to comment/correction @BenIzd ) DeleteCases[tuples, _?(Apply@Function[{a, b, c}, a + 2 b + c == 0])] is what you are looking for?
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6 votes

How to simplify function with Abs?

Try this: Refine[Simplify[mylist], Assumptions -> x \[Element] Reals]
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6 votes
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How to simplify function with Abs?

PiecewiseExpand does it. Edit and // ComplexExpand // Simplify does it ...
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6 votes
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While inside a function body does not work as expected

You may wish to disambiguate your description as it seems you're creating rational functions made up of polynomials. Below I modularized CreateDiscontinuityPoly ...
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  • 1,084
6 votes
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How to add ticks for mesh?

Use Solve or NSolve to find all the intersection points and use Epilog to add all the lines ...
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5 votes
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Replacement, PatternTest, Module related Question

The reason your attempt fails is that at the time the Function is applied to its arguments, m has not yet been replaced by ...
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  • 23.4k
5 votes
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Classifying elements, by the value of a fixed function, using Replace

L = Table[ConstantArray[1, RandomInteger[999]], 100000]; m = Replace[L, {x_List :> Quotient[Length@x, 100]}, {1}]; $$\{7,2,8,8,6,5,1,5,2,1,1,3,6,7,2,4,7,2,1,8,...
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5 votes

How to simplify function with Abs?

Here's the ComplexityFunction way I referred to in my comment just to illustrate the alternative: ...
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5 votes
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Tallying over columns of matrix

Not sure what would be the best representation in your case, but here's a possible way to start. Let's start with a simplified case of one isolated column (as a List): ...
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  • 3,717
4 votes

How to test a recursive formula using Mathematica?

For a fully recursive implementation, for which @kenric gives an outline, the definition must be inductive. In particular, you need a base case (or more in some cases, like for the Fibonacci recursion)...
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  • 213k
3 votes
Accepted

RunProcess : Save directly to Mathematica Variable

It might be possible to do what you say, if myprogram.exe can output the image data directly to stdout. But I wouldn't lose any sleep over having to create a ...
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2 votes
Accepted

Create list with integer partitions satisfying some conditions

Here is a quick and dirty code that should do what you want: For an example we choose: n = 2; m = 8; Then: ...
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  • 24.3k
2 votes

How to remove duplicates from a pair with some conditions?

Here's a stab, but I suspect it can be made more elegant. I'll walk through the development step by step before putting together a complete function. ...
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  • 3,717
1 vote
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get positions satisfying multiple criteria

Granted that your example may not be actually representative of what you ultimately want, here's an attempt: ...
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  • 3,717
1 vote

How to generate all commutative pairings of list elements?

Here is one more recursive answer that I find slightly easier to read: ...
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  • 2,791
1 vote

Function that Generates all Normal Subgroups of a Group

When the number of orbits is small, this solution is work: ...
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