Questions tagged [iterators]

Questions on using and specifying iterators used in Mathematica functions.

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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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1answer
100 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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0answers
32 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. ...
4
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1answer
127 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 ...
6
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2answers
216 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 ...
4
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3answers
286 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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1answer
37 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? ...
2
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2answers
107 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 ...
3
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1answer
127 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 ...
2
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1answer
49 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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0answers
54 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 ...
0
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2answers
71 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 ...
1
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1answer
171 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_{...
2
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2answers
109 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....
1
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1answer
53 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 ...
5
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1answer
111 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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1answer
93 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] ...
1
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1answer
30 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-\...
1
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1answer
67 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 ...
6
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1answer
391 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 ...
1
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1answer
193 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 ...
8
votes
1answer
190 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. ...
4
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1answer
91 views

Iterative comparison between different vectors

I have some soccer outcomes for each league round to import in a data form similar to that: ...
2
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1answer
67 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 ...
3
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1answer
65 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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1answer
115 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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0answers
60 views

Is it possible to generate iterators dynamically during parallel processing?

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

Iterating with Do rather than NestList

This code below works fine for me. ...
0
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1answer
65 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: ...
2
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2answers
79 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 ...
4
votes
1answer
282 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 ...
1
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2answers
52 views

Nested Table With Iterable Bounds

I have a set of data that looks vaguely like this: ...
1
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1answer
42 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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2answers
75 views

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

Update A very crude attemp ...
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1answer
171 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: ...
1
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0answers
85 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 ...
4
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3answers
528 views

Dot products and For-loops

I'm taking a class where we're working with matrix applications inside of Mathematica. In this case, we're analyzing senatorial votes that have been numericized so that a value of 1 corresponds to "...
1
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2answers
96 views

How can I iterate across a list of triples?

i just started to use Mathematica and I`m completely new to programming. So i'm some kind of noob in the purest form.. I'm trying to transform a coordinate system into a different one. I'm using <...
0
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1answer
121 views

Creating matrices using a Do-loop

Here is an image of current assignment; I am not able to do step 6 to 8 When I try to do the Do-loop, it states that the {i, j} does not have appropriate bounds. ...
1
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1answer
54 views

ListCountourPlot does not show any result [closed]

I was trying to show the heat conduction of Laplace equation problem.But the plot does not show properly ...
1
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1answer
82 views

Defining iterative algorithms [closed]

Assume the iterative algorithm of interest to be as follows: ...
1
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2answers
648 views

Multivariate Newton-Raphson method and FindRoot module [closed]

Let's suppose that we have the following equation ...
2
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1answer
468 views

Golden section search method that terminate after $n$ iterations

I am attempting to code a program that executes the golden section search method, and I would like to terminate the computations after $n$ iterations, where the user decides what $n$ is. My code works ...
12
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3answers
519 views

How to programmatically specify multiple iterators?

How to use Row[Table[{B[i],0,i},{i,0,2}],","] directly in Do command? I mean that the following command ...
3
votes
1answer
1k views

Encountering 'Error: Set::setraw: Cannot assign to raw object' during procedural function definition

Sorry for the rather vague title, but I don't know what is wrong with my code. Here is a Ruby version of what I'm trying to do: ...
2
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1answer
140 views

How to change the dimension of a tensor inside a loop using XAct/XTensor?

I'd like to define a function CDOrder[k] to compute the k-th order covariant derivative of a vector ...
0
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0answers
133 views

Operation on sublists with multiple arguments

I have a list and add only the values which are > 0 with: Total[Cases[mylist, x_ /; x > 0]] How to do this if I now have a list of sublists? ...
4
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2answers
132 views

use Range to form a vector

I have a function y[k_]:={0,0,0,I*t^k}; and I need to get a vector Join[y[1],y[2],y[3],y[4],y[5],y[6],y[7]] and it is just ...
6
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4answers
584 views

Applying loop functions with input list of iterators

Given an iterator, I am trying to generate a table of all possible pairs of values. The form of the iterator I'd like fixed, because I want to run other loops with it as well. The closest to what I ...
0
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0answers
113 views

Iterating a Module

I have a Module that can act on other Modules, which is given as Kk[EE,p,z1,z2,z3,K_func] and I am trying to iterate it, such that ...