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 ...
- 94.9k
11
votes
Accepted
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]
- 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]
- 14.8k
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?
- 36.4k
6
votes
How to simplify function with Abs?
Try this:
Refine[Simplify[mylist], Assumptions -> x \[Element] Reals]
- 3,738
6
votes
Accepted
How to simplify function with Abs?
PiecewiseExpand does it.
Edit and // ComplexExpand // Simplify does it
...
- 15.2k
6
votes
Accepted
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 ...
- 1,084
6
votes
Accepted
How to add ticks for mesh?
Use Solve or NSolve to find all the intersection points and use Epilog to add all the lines ...
- 30.6k
5
votes
Accepted
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The reason your attempt fails is that at the time the Function is applied to its arguments, m has not yet been replaced by ...
- 23.4k
5
votes
Accepted
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,...
- 14.8k
5
votes
How to simplify function with Abs?
Here's the ComplexityFunction way I referred to in my comment just to illustrate the alternative:
...
- 213k
5
votes
Accepted
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):
...
- 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)...
- 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 ...
- 62.7k
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:
...
- 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.
...
- 3,717
1
vote
Accepted
get positions satisfying multiple criteria
Granted that your example may not be actually representative of what you ultimately want, here's an attempt:
...
- 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:
...
- 2,791
1
vote
Function that Generates all Normal Subgroups of a Group
When the number of orbits is small, this solution is work:
...
- 23.2k
Only top scored, non community-wiki answers of a minimum length are eligible