Questions tagged [functional-style]
Questions about Mathematica's functional programming style, including the use of pure functions (Function[], #, &) and functions such as Map, Apply, Nest, and Through.
458
questions
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Commutator for Solving Coefficients in a Hamiltonian
I am relatively new to Mathematica but I understand the basics.
I want to solve for coefficients by commutator constraints and I have problems implementing the commutator. The setup is the following:
...
- 1
6
votes
7
answers
372
views
Removing duplicates between sublists
I want do delete from each sublist those elements which are contained in one or more of the other sublists. The surviving elements must maintain their original order of appearance.
...
- 40.6k
8
votes
6
answers
427
views
Accumulate up and down
I want to accumulate positive and negative values separately.
dt = RandomSample[Range[-10, 10]]
{3, -5, 2, -9, 1, -1, 0, 8, 10, 4, -7, 7, -8, -3, 6, -4, -2, 5, -10,...
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9
votes
9
answers
651
views
Partition a random sequence composed of three numbers
I want to partition an array composed of 1s, 2s and 3s in such a way that,
going from left ...
- 40.6k
3
votes
4
answers
208
views
Add missing column keys
Example data:
data = {{"1", 50}, {"1", 60}, {"1", 40}, {"2", 15}, {"3", 18}, {"3", 18}};
The first ...
- 40.6k
9
votes
4
answers
624
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Smooth a list of integer values
I want to smooth a list of Integers so that outlying values
become less spiky. The result vector must again contain Integer ...
- 40.6k
7
votes
6
answers
345
views
Replace duplicate list values with unique elements
My request is a follow-up on this question:
Replacing duplicates instead of deleting them
What if we want to replace duplicated values not with a single value but with newly created values distinct ...
- 40.6k
5
votes
2
answers
262
views
Create unique position values
Given a list of integers I want to create unique position-values. The following rules apply:
Take first number. If first number exceeds list length, take 1.
Take next number.
If next number is lower ...
- 40.6k
4
votes
2
answers
165
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Two simple vector partition rules
We have a vector of zeros and other numbers, f.e:
vector = {0, 0, 0, 9, 0, 2, 0, 5, 0, 4, 0, 5, 6, 2, 0};
The two rules:
Partition the vector in such a way that (1)...
- 40.6k
4
votes
1
answer
103
views
Function[0], Function[,0], and Function[{},0]: Is there any inherent distinction in the "academic" sense?
Note that Function[,0] is by default interpreted as Function[Null,0].
The following three calls all give ...
- 385
4
votes
2
answers
244
views
Enumeration of a nested list
My problem is consisting of following:
I have a nested list of following form:
{{B, v ** v, b ** B}, {b, B ** b}, {b ** B, v ** v}, {}}
And I want to enumerate ...
- 67
0
votes
1
answer
41
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My three demo script is too slow switching tabs
My three demo stripped down script runs fine but takes 6 sec to switch from demo 2 or 3 to demo 1. Actually I need nKs = 7 which takes 30 sec. I can't find examples of slow switching tabs.
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5
votes
2
answers
227
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How to Vectorize this Function?
I have been puzzling over how to vectorize the following function:
...
- 379
2
votes
0
answers
97
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How to write 2D finite volume solver in a functional approach?
I'm solving 2D poisson problem of a finite volume problem using TDMA.
The solution of the problem is given:
\[Phi][x_, y_] := x^2 y + x y^2 + 1
The definitions are ...
- 41
3
votes
1
answer
109
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MapApply Operator Form
I have a list of matrix sequences (list of matrices) that I want to multiply, something like
...
- 153
2
votes
2
answers
82
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Would it be slower to place function definitions inside another function definition?
Will it be slower to place functions' defintions inside a main function? I usually do that if the subfunctions are short.
However, with a long subfunction I usually place it outside as I think that ...
- 431
4
votes
4
answers
160
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How to I know how many nested functions have been called?
I have two functions, and the 1st calls the 2nd:
f[x_]:=Block[{},x^2]
g[y_]:=Block[{},Sin[f[y]]]
I would like to know, in each ...
3
votes
3
answers
400
views
0
votes
1
answer
42
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3
votes
3
answers
417
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How to make a function take another function as an input?
I am quite new to mathematica, and I simply want to know how to make a custom function, take another arbitrary function as an input.
I have attached code that shows what I am trying to accomplish (...
- 125
0
votes
1
answer
92
views
Create a function that can assign values to different variables in Mathematica
Here I am trying to create a function that can assign values to different variables in Mathematica.
Assume the function
f[a _, b _, c _];
x1 = a;
x2 = b;
x3 = c;
...
- 51
2
votes
1
answer
161
views
Can it be rewritten in a less abbreviated version? [closed]
I am trying to understand this code
...
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9
votes
6
answers
350
views
Map function to the list and keep the previous
Give the following list,
list = {{a1, a2, a3}, {b1, b2, b3, b4}, {c1, c2, c3, c4, c5}};
I want to get
...
- 5,562
1
vote
0
answers
34
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How to create a Sort function that does not differentiate between String rule keys and Symbol rule keys
Im trying to Sort Rule-s according to Key-s (or names) but the normal ...
- 2,397
3
votes
1
answer
154
views
How to replace a multiple iterator Table to speed up computation
I need to create an array of data which resembles to something like this
Table[{i, Sin[j^2*i]}, {j, 2000}, {i, 0., Pi, Pi/10000.}]
where each "row" of ...
- 953
2
votes
0
answers
32
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Attributes for functions with currying [duplicate]
Is there a way to set attributes for a function which holds for all arguments when currying?
When evaluating, e.g.,
...
- 1,460
1
vote
1
answer
144
views
Cannot find DockedCells with Cells or NotebookFind
Request 1: A workaround for Cells or NotebookFind needs to be found for locating and returning the ...
- 2,397
10
votes
1
answer
222
views
How to programmatically construct a function or a compiled function?
I'd like to programmatically construct a function from a long expression with many duplicate terms. The objective is to programmatically create a set of compiled functions with expressions that were ...
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23
votes
3
answers
1k
views
What is the fastest method to set the diagonals of a matrix to 1?
I am trying to replace the zeros along diagonal of a distance matrix to a list of constants. In this case, a diagonal of 1's.
It appears that the LinearAlgebra ...
- 3,926
4
votes
1
answer
81
views
Accumulate[] on an ordered HashTable
Hopefully this is a trivial question, but I keep getting lost looking for an answer in the documentation.
I have an ordered HashTable containing indexed real numbers:
...
- 143
1
vote
0
answers
88
views
Numerical solution for multi-step PDEs
I am trying to numerically solve the following PDEs in MMA (v12.0)
$$\partial_u f(x,u) =
\left\{\begin{matrix}&-a f(x,u) + b \, \partial_x^2 f(x,u), & 0<u<T\\ &r(x;\alpha_1) \, f(...
- 231
1
vote
1
answer
100
views
While inside a function body does not work as expected [closed]
I'm trying to write a function that return a randomly created rational polynomial function that has a discontinuities points.
I already have a function that generates random rational polynomial (...
- 69
6
votes
4
answers
375
views
How can I efficiently define functions with different names but doing the same stuff?
Recently I have met with with this interesting question:How can I efficiently define functions with different names but doing the same stuff? Somebody may want to ask me why I want to do things like ...
- 463
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votes
0
answers
56
views
Algorithm consisting of modules returning multiple errors
I'm trying to write a genetic algorithm that will take a list of lists of reals in interval [0,1], my "starting population", "score" them according to a fitness function, append ...
- 65
6
votes
1
answer
127
views
K-Mean Clustering Algorithm
I have implemented the k-Means Clustering Algorithm using the Wolfram Language. However, I think it can be more efficient. Do you have any idea how to make it more efficient (e.g., by removing the ...
3
votes
5
answers
217
views
How can I get a list of all distinct unordered pairs of numbers in a specific range? [duplicate]
If I do e.g.
Flatten[Outer[List, Range[3], Range[3]], 1]
I get
...
- 369
2
votes
1
answer
337
views
What's a functional alternative to nested Do loops?
How can I use functional code to achieve the same effect as the following procedural code
Do[
Do[
f[i,j],
{j,1,m}
],
{i,1,n}
]
- 369
7
votes
1
answer
202
views
How can I do "Map" on a binary function?
If there is a one-variable function, we can f/@{a,b,c} to get {f[a],f[b],f[c]}
What to do with it if it comes to a binary ...
- 337
5
votes
2
answers
453
views
Map a two argument function to every element on list
I'm new to use the amazing map function in Mathematica, and I've found it really elegant to program in simple lines of code. However, I'd like to perform more elegant stuff. I've found this question, ...
- 673
4
votes
4
answers
247
views
Successive chunking of a list
I have shuffled and used the output of Range[20] in order to create this minimal example:
t = {19, 4, 12, 1, 17, 13, 7, 14, 10, 11, 6, 18, 20, 15, 16, 3, 8, 5,
2, 9}...
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14
votes
7
answers
820
views
Iterate over # without needing to define a variable
I want a function that takes in a number $n_0$ and a list $\{n_1, n_2, n_3, n_4, n_5\}$ and returns $\{\{n_0,n_1\},\{n_0,n_2\}, \{n_0,n_3\},... \}$. The reason I want this is to use it in Map, so I ...
- 558
7
votes
2
answers
190
views
Is Function broken is this example?
This program
f[x_] := g[Function[a, x]];
g[fn_] := Module[{h}, h[a_] := fn[a]; h[0]];
f[999]
returns
Function[0, 999][0]
but ...
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11
votes
3
answers
687
views
Function that does for Map what Through does for Apply?
Through allows multiple functions to be easily applied to a single argument. For instance, suppose I wanted to count the number of characters in ...
- 3,568
1
vote
0
answers
26
views
Is it possible to insert a fixed-size Input Cell in a DockedCell toolbar that directs output if any to a specified Cell in same Notebook?
Ive been coding Mathematica for over a year but this language can do so much more than any other language hence beginners really do need a much longer gestation period. That is why this rarest of ...
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0
votes
2
answers
107
views
How to declare that a function is arbitrary then specify them later? [duplicate]
I need to evaluate an expression, sum in this case, involving an arbitrary function. Below is a simplified version of what I wanted to do:
...
- 63
0
votes
1
answer
187
views
How to use the Wolfram Language Symbol entity type to list all the entity types? [closed]
I would like to map EntityValue[#,"SampleEntities"] over all the domains of entities, but before I spend 20 to 30 minutes typing every single entity, I would like to be aware of any way to ...
- 1,653
0
votes
1
answer
62
views
How to find all functions that accept level specifications as an argument?
How can I find a list of every function that takes a level specification as an argument?
- 1,653
2
votes
1
answer
69
views
Seeking for a general method to turn the term(s) in a formula into a list [closed]
If we want to make arbitary formula into a List, for example, input (1+a^3) and we want the output data to be {1,a^3}, we can use List@@(expr). However when input data becomes a^3, we need to change ...
- 77
0
votes
0
answers
41
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Finding the integer values of $p$ and $l$ for which a function $b(p, l)$ is divisible by $n$
I wrote the code in the attached image to find the integer values of $p$ and $l$ for which a function $b(p, l)$ is divisible by 3. Does anyone know of a nicer way to achieve the same result? Perhaps ...
- 283
2
votes
1
answer
104
views
Considerations for Compiling and Parallelizing Code Outside or Inside Map[]
Assume f as well as Map[f,list] are parallelizable and compilable, such that parallelization and compilation give significant ...
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