Questions tagged [list-manipulation]

Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.

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3 votes
1 answer
47 views

Plotting Individual Variables from RandomFunction

I have defined an Ito Process such that: ...
2 votes
1 answer
75 views

Table range as disconnected interval

I wish to evaluate table entries but with the dummy variable taking values in separate intervals. For instance, instead of writing ...
1 vote
1 answer
59 views

Efficiency on array iteration

Consider a 2-d array n by n of the form array1 ={ {x11,x12,x13,...,x1n},{x21,x22,x23,...,x2n},{xn1,xn2,xn3,...,xnn}}. I want to expand every point in this array in ...
2 votes
1 answer
88 views

Minimize Sum of Hamming Distances

Problem: Given an $n \times m$ matrix with binary values $(0,1)$, find a binary vector that minimizes the sum of Hamming Distances to the rows. Example: If the matrix is {{$1,1,1$},{$0,0,0$},{$1,0,1$}}...
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3 votes
2 answers
89 views

Finding the consecutive distance of n-dimensional points with Mathematica

I want to create a list of (n-dimension, average of points) with 10,000 points per n-dimension. I can't figure out how to take the distance of consecutive points. Say in 2-dimensions, there are 3 ...
1 vote
2 answers
107 views

How to generate a numerical table?

I have the following issue for generating a table in Mathematica. How to generate a table with the limits 10^-18 to 10^-6 with steps of (1,2,3, ....10)*10^-1? e.g. It should look of the following form:...
  • 125
3 votes
2 answers
111 views

Get the coordinates from RegionPlot3D

I have a plot generated with RegionPlot3D and need to extract the coordinates of the points on the plot. I'm trying to apply the approach from this question about RegionPlot to RegionPlot3D but it ...
  • 133
0 votes
0 answers
48 views

Droping a row from a matrix [duplicate]

I want to drop a row from a matrix but the output seems to be: MatrixForm[] My code: ...
  • 1
6 votes
4 answers
836 views

Implementation of MATLAB's "numgrid" function [closed]

I am looking for an implementation of MATLAB's numgrid function, in particular the "B" mode. For example, I want to get the matrix corresponding to the ...
2 votes
1 answer
69 views

Sorting of a list of lists - i.e. list of matrices - what is the order of the sort determined by?

In the documentation we have: Sort[list] sorts the elements of list into canonical order. Maybe I am missing something but what does "canonical order" mean for sorting a list of matrices? ...
  • 525
5 votes
3 answers
163 views

How to map a function across multiple ragged lists

Preliminaries I have lists that are lists of lists (i.e., each list contains one or more sublists and are ragged (i.e., each sublist can have a different length, though all have a length of 1 or ...
  • 9,505
5 votes
3 answers
211 views

matrix Crop (remove leading and trailing zeroes in matrix)

I have some matrices that have 0's around them, for example, give such a matrix MatrixForm[ mat = ArrayPad[{{1, 2, 3}, {0, 0, 0}, {7, 8, 0}}, {{1, 2}, {2, 3}}]] \...
  • 4,994
1 vote
2 answers
88 views

How to assign table parameters to use it many times

I'm using two nested Table to generate data which depend on two parameters, let's say it is temperature and pressure, many times in my code. When I change the temp ...
  • 95
3 votes
1 answer
174 views

Generating a non-convex polyhedron from polygons and normals

I am working on developing "directional offset" module, which requires pretty tricky mesh generation: offset values vary in different directions. Suppose I have list of points and polygons, ...
  • 303
1 vote
1 answer
62 views

Draw the values of two variables each on a axis in a square

I plot lists of {xA1} over time and lists of {yB1} over time. Now, How can I draw two lists {xA1} and {yB1} so that the values of each are shown on a separate axis inside a square? (same as below ...
  • 77
0 votes
1 answer
64 views

Pulling Results from NDSolve within a Table

I am still learning the intricacies of Mathematica. I have an NDSolve within which I am trying to vary a specific parameter (I understand that ParameticNDSolve is likely a more efficient tool--the ...
  • 31
0 votes
0 answers
29 views

DiscretePlot with a List as argument [duplicate]

Suppose I have some multidimensional function that is computationally very expensive to evaluate. Here, I will just use ...
  • 101
0 votes
2 answers
39 views

How to replace the 6th column with another column? [duplicate]

Consider the following table: tabb = Table[RandomReal[{0, 100}, 100], {i, 1, 10, 1}]; How to replace its kth column (say, the 52th column) by the column ...
  • 4,116
2 votes
2 answers
143 views

Add quotes to each element in a list

How to add quotes to each element in a list? For example, we have a list as: ...
  • 513
1 vote
0 answers
57 views

An error in the short form of a two-dimensional array?

I noticed very strange behavior in the function Short when applied to a two-dimensional list of real numbers in Mathematica 12.3. Consider that ...
  • 101
0 votes
1 answer
79 views

Plot two list for differen first list parameter

I have a series of equations based on which I plot final lists of "xA1","yB1". I need to change "xA1 = {0.55}" and "yB1 = {0.6}" between [0,1] with interval 0....
  • 77
3 votes
3 answers
158 views

Find first position satisfying condition, which is true after a certain element

Can we find the first position of elements of a list satisfying a condition, with good performance, if the conditions is a tail condition of the list. What is tail condition ? (the term is informal, ...
  • 3,221
0 votes
1 answer
64 views

Why the performance of list of Timings depend on the order?

It seems that the result of list of Timings and AbsoluteTimings depends on the order, while ...
  • 643
11 votes
2 answers
449 views

How can I create an atomic head or treat some head as atomic during Map?

For example, Map[g, {0, {h[1, 2, 3]}}, {-1}] gives {g[0], {h[g[1], g[2], g[3]]}} I want a ...
  • 16.4k
2 votes
2 answers
56 views

Multiple columns from a single column of data file

Suppose I have a data file containing one column of 1000 rows having x, y, z and ϕ values. I need to separate them into four distinct columns by selecting every alternative value. For example, if I ...
  • 664
1 vote
1 answer
52 views

How to select in the following way?

Consider the following nested list: fff = {{1, 2, {{1, 2}, {3, 4}, {19, 20}, {21, 22}}}, {2, 8, {{0.5, 3}, {1.4, 2}, {3, 13}, {2, 18}, {0.3, 19}, {20, 21}}}} ...
  • 4,116
7 votes
8 answers
453 views

How to replace anti diagonal elements of a matrix

I want to assign new values to the anti-diagonal elements of a square matrix m with the values of its diagonal elements. For that, I want to make use of ...
  • 319
14 votes
2 answers
145 views

Help understanding a bug when FoldList using RandomChoice is Compiled

Bug introduced in 3.0, persisting through 13.1. Preamble: I submitted this bug to support@wolfram.com and it was acknowledged. I assume it will be fixed eventually. In the meantime I'd like to ...
  • 1,549
1 vote
1 answer
98 views

Convert List to Matrix [closed]

I have the lists in matrix form, as shown in the screenshot fig.2 below. I would like to convert it to pure matrix like fig.1 Edited: For example: ...
  • 143
1 vote
1 answer
57 views

How to efficiently rearrange elements in big data file? [closed]

I have this data and would like to rearrange the element in a specific way, I used Table but it tasks time 12 sec, is this ...
2 votes
2 answers
83 views

Selecting terms from a list based on certain pattern

I have the following table: ...
  • 357
1 vote
1 answer
65 views

Table mix with If function [closed]

Anyone could explain to me which problem is? after running the function "Table" combining with "If" as below, but the result is not a value instead. ...
  • 143
1 vote
2 answers
184 views

Generating Lyndon words modulo mirroring operation and substituion

I have two letters A,B. I want to generate all words say up to length 22 with the following properties. There is no "canonical" list so any such list will suffice, though there are many ...
  • 635
1 vote
2 answers
77 views

2D Scatter plot with z-value used for PlotLegends

I have a data set that can be generated as follows: x=RandomReal[{1,5},100]; y=RandomReal[{11,50},100]; z=RandomReal[{7,25},100]; For each of the (x,y,z) 3-tuple, ...
  • 107
4 votes
3 answers
110 views

Write the result of expression to a list [closed]

I have a question. I want to write the result of the expression such as y=2cos(n.Pi/3) for 100 values n into a list. Could you tell me which code I should use?
  • 143
4 votes
2 answers
113 views

Unexpected behaviour of Condition with Cases/MatchQ?

When using the unsorted version of Complement in this question I met the following unexpected result, ...
  • 643
2 votes
3 answers
141 views

Divide string into a sublist of sentence with the maximum number of character

Context: I have a long article (on Wordpress). And I'm using Google Translate API (v2) to translate this article. This article has about 300 000 characters. However, due to the limit of Google ...
  • 1,701
4 votes
1 answer
44 views

Timing Discontinuity with Replace[] Function

When constructing certain square matrices I noticed a sharp jump in the time required to build them. I've included code and a plot of time required to make the matrix vs dimensionality of the matrix. ...
5 votes
4 answers
581 views

Replacing large numbers

Imagine I have the following list l = {{1,2,3},{4,10^(16),5}} How do I efficiently replace the large number by a number (zero, for example). I can't seem to do it ...
  • 4,388
5 votes
2 answers
358 views

How to generate a list of random numbers with conditional statements

I want to generate a list of numbers with certain conditions. Eg. First I generated 10 random numbers between 1 and 20. M1= RandomReal[{1,20},10] Now I want to ...
  • 107
9 votes
3 answers
656 views

What is the best method to search pattern for 2D list?

What is the best method to search patterns for 2D list ? Let L be following 2D-list : ...
  • 3,221
8 votes
2 answers
313 views

Simple, fast re-defining a part of 2D list

A[[{2, 3, 5}]] = {97,98,99} changes 2,3,5-th elements of A to 97,98,99 respectively. Similary A[[{2, 3, 5}]] = 100 changes 2,3,...
  • 3,221
3 votes
1 answer
54 views

Piecewise Functions from List of Functions

I have multiple functions from two different NDSolves that I would piece together. Here is a working minimal example: ...
1 vote
1 answer
66 views

Why does my simple string function fail to grab the only element in a List?

The idea is to normalize a string before processing it to extract information from it. Strings may come with embedded outer brackets which are easily stripped or as elements of a true list. This is ...
  • 1,977
2 votes
1 answer
98 views

Loop over multiple variables with readable code

I've seen similar posts to this, but not with as many variables. I need to loop over 8 variables, with only two values each(1 and 2), so I can loop over the 16 possible input and output states, and ...
11 votes
6 answers
647 views

How can I multiply only a few columns of a table by some number in a compact way?

Consider a table tab = Table[{i,i^2,i^3,i^5,i^0.3,i^0.7},{i,0.2,3,0.1}]; I would like to multiply the 2rd and 5rd columns by some number. This is how I do it: <...
  • 4,116
0 votes
1 answer
39 views

Generalised KroneckerProduct that works like Outer[] [closed]

Is there a Mathematica function that works like this: Function[f, A, B] where f is a function with two arguments, and ...
  • 103
3 votes
3 answers
108 views

Parsing an expression for coefficients and more

I have many expressions of this form: ...
7 votes
2 answers
111 views

Doing ArrayReshape in Mathematica doesn't give desired results

I have an array like this for example, a = ArrayReshape[Range[16], {4, 4}] \begin{align} \left( \begin{array}{cccc} 1 & 2 & 3 & 4 \\ 5 & 6 & ...
  • 519
1 vote
3 answers
68 views

Modifying list of lists to standardise lengths and field positions

Sorry, beginner here. I feel this should be simple but I'm struggling... I'm reading a set of race timing data from a web site and want to manipulate it into a list of lists that I can then export to ...
  • 185