Questions tagged [iterators]

Questions on using and specifying iterators used in Mathematica functions.

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Efficient alternatives to a Table based iteration

I have performed some operations using the Table iterator but I am looking for efficient alternatives to my approach. First, some preliminary code: ...
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39 views

How to implement recursive function in While loop Module, calling on other functions

I am trying to implement a module such that it " takes a distance matrix, Q, and iterates the corresponding “Bellman operator” module written above until a final cost-to-go function (i.e. J) is ...
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2 answers
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In a for loop, how do I assign a table of values to a new variable for every iteration?

I am trying to create a divided differences table for a set of data of depth n, specified by the user. I am not sure how to create and assign a new variable name for each iteration of the for loop. ...
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2 votes
3 answers
249 views

Nested floor functions

I would like to compute a limit involving a particular nested floor function. For example: ...
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1 vote
3 answers
57 views

Digits product and an iteration process

I would like to create a code which gives me the square of the product of the digits of a number, with the only rule that if a number has a 0, then it doesn't count in the product (for example, if the ...
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2 votes
0 answers
23 views

Constructing Table iterators programmatically: how to avoid the non-list iterator error? [duplicate]

The following simple code of course works: Table[n^2, {n, 3, 15, 2}] (* Out: {9, 25, 49, 81, 121, 169, 225} *) I would then like to construct the iterator ...
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6 votes
5 answers
295 views

Changing iterator inside a Table?

Consider Table[ If[i == 3, i = i + 2;]; i , {i, 1, 10}] {1, 2, 5, 4, 5, 6, 7, 8, 9, 10} The above output is not what I would expect (namely ...
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3 votes
2 answers
113 views

Generate a sequence of all cases

There is a sequence of numbers that satisfies $a_1=2$, $a_n-a_{n-1}\in \{1,3,5\}$ I tried to enumerate all possibilities using the code below ...
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6 votes
0 answers
84 views

WTC2021 Iterators Paclet download

At WTC2021 Roman Maeder gave a presentation about Iterators. In the presentation notebook it is mentioned that the code / paclet (Iterators-0.9.paclet) is provided as part of the presentation ...
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1 vote
0 answers
29 views

Repeated calculation with neural network measurement slows down

I have a list of 200 neural nets nets0. I have to measure the output of several layers of each of them on a list of 1000 associations ...
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  • 195
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38 views

Generating iteration and constraint lists dynamically

I have a model for which I want to perform a set of calculations with successively deeper iterations and more constraint. In other words for a given value of a Do iterator, n, I want to: perform a ...
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  • 201
2 votes
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60 views

Supplying a seed for an iterative method in LinearSolve

Just a quick question. Does anyone know if it is possible to supply a seed for the iterative methods in LinearSolve? I have a large sparse system, and even using some Krylov iterative solver, my ...
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5 votes
1 answer
131 views

Incorrect syntax highlighting? "Variables made special by use in arguments" not working

This example is obviously not useful on its own, but it will cover everything I actually need to know for a more complicated function I'm making. The example is to recreate the ...
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2 votes
3 answers
123 views

Exporting specific frame of ListAnimate

Imagine I have a certain list of Graphics-type objects that I then incorporate into ListAnimate ...
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  • 4,138
0 votes
3 answers
122 views

Iterative function

I would like to write a bit of code that does the following. Pick a random number from 1 to 20 (inclusive) then if that number is < 15, stop if that number is > 15 pick 2 numbers from 1-20, and ...
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  • 676
2 votes
1 answer
137 views

Repeating and Sequencing Procedures with two Do-loops

I have a Do loop where I'm looking for the value of certain parameters that respect the conditions inside an If, and with those values, a run another Do to make another calculation of an expression ...
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1 vote
0 answers
40 views

Custom Table, for iterating over permutations

It is common that I iterate over all permutations of 1,2...,n, either by making a table or performing a sum. Instead of creating the set of all permutations, it would be better to iterate over them. ...
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4 votes
1 answer
145 views

Trouble iterating my forest fire simulation

I'm having some trouble iterating my simulation of a forest fire. I'm new to Mathematica, so apologies for poor coding. I'm sure there are far neater and more efficient ways of doing this, but I would ...
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6 votes
2 answers
232 views

Function to create random matrix, then a simulation. *EDIT* Create two functions

How can I write a function with parameters b, i, and j, which would return a i x j array of 0s, 1s, and 2s, but the array needs to be populated randomly with 0s and 1s which have respective ...
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4 votes
3 answers
302 views

Function representing a forest fire after one time step

How can I create a function that would have as its argument an array mat of 0s, 1s, and 2s where the 2s are burning trees and the function would give an array that represents the forest after one time ...
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  • 327
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1 answer
51 views

solve for variable in iterator limit

Why can we not solve for P in the iterator limit in the problem below? How can it be solved? ...
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2 votes
2 answers
131 views

Can one make `Do'-Loops of arbitrary depth?

In the documentation for the Do[...] function, a loop of nesting up to any number of layers is supported. But to apply their function, one needs to know ahead of time how many layers of loops they're ...
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  • 163
3 votes
1 answer
141 views

Strange indexing behavior by Table

Maybe I do not understand how Table works, but I find this very confusing and it took me a long time to debug because this was part of a much more complicated routine. I am trying to build an array ...
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  • 594
2 votes
1 answer
52 views

Two different variables in a Do Loop

I am trying to use the code developed by @Alex Trounev here: Numerical solution of an iterative equation for different kind of q. I am not sure how to incorporate ...
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1 vote
0 answers
67 views

Need help with NestList [closed]

NestList::intnm: Non-negative machine-sized integer expected at position 3 in NestList[#1 + t&, 0, 8.]. What does the above error mean and how can I refer to result of ...
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0 votes
2 answers
109 views

Using condition for each element of a matrix

I'm trying to write a code so that for each element of matrix C2 if the element i,j is equal to element j,i and it is equal to 1 then it adds one to a variable and if not it adds one to another ...
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1 vote
1 answer
343 views

Fixed point iteration with While or Do Loop

I need to write a while or do loop to perform the iteration $x_{n+1}=Cos(x_n)$ with initial value $x_0=1$ and stops when the absolute value of the difference between two consecutive iterations is $|x_{...
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2 votes
2 answers
114 views

Using iterative functions to specifically sort a list

The following code sort the list li in a such way that consecutive terms $t_n,t_{n+1}$ are of the from ...{x_,y_}, {y_,z_}.... i....
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1 vote
1 answer
57 views

Use of a For/While loop inside another For/While loop for dual integration [closed]

Can anyone please give suggestion for using For/While loop inside For/While loop for integrating a function with respect to two variables say for- $\qquad r = (x^2 + (a/y^2))^(-1/2)$ Integration is ...
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5 votes
1 answer
112 views

Nest or fold a series of geometric transforms

I have a requirement to perform a series of GeometricTransformation[]s using the AfineTransform[] function. I use these to set ...
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  • 187
0 votes
1 answer
102 views

How I can plot the below map?

I have tried to plot the following map: $\qquad \begin{cases} y_{n+1}=r y_n^{x_{n+1}-x_{n+2}}\\ y_1=x_1-x_2 \quad \end{cases}$ using the code shown below. The error I have got is that x[1] - x[2] ...
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1 vote
1 answer
31 views

Plotting an iterated piecewise function with endogenous nodes

I am trying to plot a piecewise function that I can define recursively, where the nodes are endogenous as well. Basically, $f(l)=a^{t}$ when $l \in \left( \frac{\mu}{\alpha^{t-1}(1-\alpha)+\mu(1-\...
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1 vote
1 answer
72 views

Code to generate many Do-loops, where the $i$-th loop has upper bound given by $f(i$)

How do I get Mathematica to run an arbitrary number of Do-loops, where the i-th loop it upper bound given by some function $f(i)$? I badly need help with this. Let's denote the desired code by ...
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7 votes
1 answer
412 views

Why can't I create {a,a,a,b,b,b,b,b,c,c} from x={a,b,c}; f={3,5,2}; Thread@Table[x,f]?

ClearAll[x, f] x = {a, b, c}; f = {3, 5, 2}; Thread[Table[x, f]] produces Table::nliter: Non-list iterator f at position 2 does not evaluate to a real numeric ...
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  • 1,767
1 vote
1 answer
358 views

How do I evaluate my functions over a range of values? [closed]

I want to use the list of data which will come from MapData1 (in code); the first element is θ and second is Action(I). I want to use this Action(I) and Angle(θ) in ...
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8 votes
1 answer
224 views

How can I use a loop with an iterator in order to evaluate a function?

I'm trying to evaluate a function, that depends on two variables, in a specific set of values. I will write an example, but my system is more complicated. ...
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4 votes
1 answer
101 views

Iterative comparison between different vectors

I have some soccer outcomes for each league round to import in a data form similar to that: ...
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  • 401
2 votes
1 answer
79 views

Stop `(Parallel)Table` evaluation when wanted case is found

I have to go through a long list of evaluations, for which I suppose Table instead of For or ...
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  • 4,006
3 votes
1 answer
125 views

Making a recursive function

Suppose I have the following functions: a[x_] := x b[x_] := x (a[x]) - a[x] + 1 c[x_] := x (b[x]) - b[x] + 1 d[x_] := x (c[x]) - c[x] + 1 as you can see each ...
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  • 2,696
0 votes
1 answer
118 views

Does lower case n have some significance in the Wolfram Language? [duplicate]

I am truly confused with this one, and maybe someone could help me to clear this up. I am running a Table[] that runs multiple neural networks in series on OpenAI'...
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  • 1,397
2 votes
0 answers
70 views

Is it possible to generate iterators dynamically during parallel processing?

I have a parallel processing code written in Wolfram Mathematica, similar to: ...
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3 votes
2 answers
129 views

Iterating with Do rather than NestList

This code below works fine for me. ...
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  • 1,601
0 votes
1 answer
69 views

Problem with iterations of Prepend/While

I am doing some work with black-scholes and am trying to find random interest rates based on some given information. This is my original code: ...
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2 votes
2 answers
127 views

How to iterate through a lists of lists and delete a certain element?

Say I have a list of lists such as l1 = {{a, 2}, {a, 5}, {b, 3}, {b, 9}} How would I iterate through the list and delete all the lists with the first element b ...
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4 votes
1 answer
395 views

How to nest multiple functions with multiple variables

I'm trying to solve coupled equations by using iteration. There are two functions $G$ and $H$ that I need to find. In the code, G and H are actually lists of numbers. I start by using a simpler ...
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1 vote
2 answers
58 views

Nested Table With Iterable Bounds

I have a set of data that looks vaguely like this: ...
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1 vote
1 answer
51 views

Iterate through union of lists to correspond to each element a list of names of the lists to which the element belongs

Say I have several lists L1, L2,L3 an I want to correspond to each of the elements of Union[L1,L2,L3] a list of list names to ...
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1 vote
2 answers
79 views

How to iteratively (or most efficiently) create such list?

Update A very crude attemp ...
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  • 1,252
0 votes
1 answer
223 views

Automating a large operation by making a function

I would like to automate the following operation. To be transparent I shall put my code into separate chunks and explain the process. Suppose I have the following: ...
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  • 2,696
1 vote
0 answers
86 views

For- loop which can reuse updated values [closed]

Eout = E^x ; For[kz = 1, kz < 4, kz++, Print[Eout1[kz] = Eout]; Print[kz]] The output is E^x 1 E^x 2 E^x 3 But what ...
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