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
3answers
40 views

generating lists of integers with constraint

Suppose you have the list $a=(k_1,k_2,k_3, \dots, k_N)$ such that $k_{i}\; (i=1,\ldots, N)$ are non negative integers. How can you get all the lists that satisfy the constraint $\sum_{i=1}^{N} k_{i}=M$...
1
vote
1answer
31 views

list elements as indices

I have the list R: ...
11
votes
9answers
864 views

list-array construction

I want to create the list ix={1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4} I can do ...
2
votes
2answers
171 views

Delete a range of elements from a list [closed]

If I have a list of 100 integers, say {1,2...100}, and I wished to delete all elements that are greater than a random integer $n$, what command should I use for ...
3
votes
2answers
146 views

Extract Parts of a Function

I have an expression of the form a Integrate[b[t], {t, 0, x}] and I would like to take the coefficient $a$, save it to a list, take the $b(t)$ out of the ...
3
votes
2answers
133 views

Replacing a random ith row and column from a matrix

Currently I am trying to delete a randomly-chosen $i^{th}$ row and column from a square $n \times n$ matrix $A$. So far I come up with the following code: ...
5
votes
4answers
137 views

How to drop/extract elements of a list which starts with Plus

I have the following list : list={a^2, b^2, a^-1, a^2+b^2, (a+b+c)^-1, (a+b-c)^-2} Do[Print[list[[i]]//FullForm],{i,1,Length[list]}] I want to break this list into ...
5
votes
1answer
109 views

ReplacePart to substitute a row in a Matrix

I have a very large n x n matrix from which I want to take a row i from and substitute every element with 0. When I try the below command however, the ith row is not replaced by a list of n zeros but ...
2
votes
1answer
198 views

How can I condense this code?

Here is part of a code I wrote: ...
0
votes
1answer
78 views

Improve running speed of FullSimplify function

How can I make this code faster? The checking with FullSimplify takes a lot of time. ...
1
vote
2answers
94 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 ...
0
votes
0answers
56 views

Correct way to format numbers

I have defined the following function: randvec[mag_]:= mag Normalize[Table[RandomReal[], {j, 1, 4}]] I would like to format the numbers in the list so that they ...
2
votes
1answer
53 views

List of all possible unions of given sets

I'm trying to generate a list of all possible unions of some sets to generate a topological space from a given basic sets. For ex: Given {1}, {2}, {4}, {1,3} I ...
0
votes
2answers
70 views

How to generate random vectors without repetition?

Say we have three elements, 0,1,2 and we want to generate 1000 random vectors of length 7 with these elements, i.e. {2,1,0,0,0,0,2} How can we do this without ...
1
vote
1answer
57 views

Generate part of peak with only initial part of peak

If I have the following data: ...
0
votes
0answers
53 views

Appending to a list in a For-loop

I am new to Mathematica. Here is my problem: Given the matrix $\qquad M = \begin{pmatrix} 2 & -1 \\ 1 & 2 \end{pmatrix}$, sum the overlap (inner-product) of it's eigenvectors $\qquad \bigg\{\...
-1
votes
0answers
45 views

Rotate and translate previously-plotted data

I have the following: Show[data1, data2, data3,PlotRange -> {All, All}] where data1, ...
2
votes
1answer
55 views

Removing certain numbers from a list

If I have an list of numbers {1, 2, 4, 70, 11, 20, 56, 79}, is there a way to remove the list {2, 4, 56} from that list? In my ...
3
votes
1answer
69 views

Remove errors from sublists after Excel import

I have a very long list such as: https://pastebin.com/9vYDLsVp At the end of each sublist for some reason I have {,-6}. How can I remove that from each sublist of ...
0
votes
0answers
32 views

Iterating MovingMap with Nest

I am trying to create a background correction inspired by the PyMca strip background method. The data I'm trying to correct is a HPLC chromatogram in the form of a ...
3
votes
1answer
101 views

Build Table of Edge Weight Sums

Is there a convenient way to build a table as generated by the code below where a 5th column (at the far right) could be added to the table that is the sum of the edge weights for the nodes in a given ...
0
votes
0answers
27 views

“Tag List in … is Protected” [closed]

I tried to plot this surface: scherk5[a_, b_, c_][u_, v_] := {a ArcSinh[u], b *ArcSinh[v], c* ArcSinh[u v]} I obtain ...
3
votes
3answers
105 views

Alternative to Inner which allows level specification

Is it possible to restrict Inner to a certain level? According to the documentation, the expected behaviour for Inner is to ...
0
votes
1answer
70 views

List Plot Error [closed]

I've produced this simulation of a superhetrodyne radio receiver. I'm pretty sure it's solid for the most part but I'm getting a list plot error. ListPlot::lpn: {{{1.,0.},{2.,0.00104953},{3.,0....
4
votes
2answers
54 views

Smart under-sampling of a large list of data points

I have dielectric functions of materials as lists of value pairs {{x1, y1}, {x2, y2}, ...} and unfortunately some of them are quite long, which is a bother in ...
0
votes
0answers
30 views

InterpolatingPolynomial: magnitude of coeffictions

I have a list of the type {{x,y},f} and want to get an InterpolatingPolynomial for that list. The x values all run between 1.3 and 2, the y values between 0 and 1. ...
8
votes
3answers
443 views

Improve running speed for DeleteDuplicates

How to make this faster? I want to remove elements that satisfy the condition below but it's way too slow. ...
-1
votes
1answer
47 views

PlotStyle options not working [closed]

I have a list of LogLogListPlots, lets name it 'Collection'. 'Collection' has i elements. When representing them all in just one plot I use: ...
5
votes
6answers
537 views

Representation a matrix as a colored square shape

I am sure that I have accidentaly seen before a way to construct a square shape corresponding to a matrix. For example if we have a 5*5 matrix: ...
4
votes
3answers
220 views

DeleteDuplicates and select which one to delete from a pair

In this case if two lists with the same total then one list is deleted. Can I add one more condition to choose which one to be deleted, for example the deleted list between the two is the one where ...
6
votes
1answer
77 views

Partitioning a list to several depths

I an aware of the Partition command which partitions a list into sublists. I'm curious as to whether there is an efficient way to partition a list several times ...
1
vote
1answer
49 views

Interactively extracting arbitrary portion of elements from a 2D list

I have a 2D list which can be plotted as follows: Image 1 Based on the plotted image, I would like to select some of the shapes on the image and extract the data for further analysis, for example, ...
7
votes
4answers
102 views

Take $ n^\text{th} $ sub-list with equal distances

I have been looking at Span, Take, etc. functions but I couldn't figure out how can I extract elements likes this ...
1
vote
1answer
61 views

Sort and extract values in a nested list

I want to sort the following nested list of peak points by the y values while keeping the dimensions consistent. I then want to extract the x value of the largest and second largest y values (if the ...
1
vote
0answers
42 views

How to specify an element of a list when using RecurrenceTable [duplicate]

My problem is that I'm trying to get a list of refraction angles in a multilayer structure (for the sake of this example - with two types of refraction indices and eleven layers of them). The code is ...
4
votes
0answers
70 views

What exactly is the difference between Part and Extract?

From the statement in the documentation: Extract[expr,{i,j,…}] is equivalent to Part[expr,i,j,…]. So basically Extract is just a listable version of ...
2
votes
1answer
66 views

Getting 1st element of a nested list, based on criteria for 2nd element [closed]

I have a list such as {{abc,1},{def,2},{ghi,1},{jkl,3}}. I would like to extract elements that have 1 as the second element (ignoring those that have 2 or 3 as their second element). In the case ...
4
votes
5answers
322 views

Randomly Choose from list but meet conditions

I have a list of integers from 0-99, but some of the integers have been randomly removed. I want to pick a random integer that is still in the list, let’s call it ‘a’ but if a+1, a+2, and a+3 are not ...
0
votes
2answers
58 views

Import and extract certain column and row

I have a problem with importing and extracting 2nd column in my CSV file. I need to have 3 list, the first one first column except for first row, the second will be second column except for 1st row ...
0
votes
1answer
99 views

Extracting values from a list

Consider these lists : ...
0
votes
1answer
137 views

Picking data from a list

For the purpose of my question, I cannot use random data. So the data are provided. ...
5
votes
4answers
186 views

Extract four (von Neumann) neighbors of a matrix entry

Assume I have a $m\times n$ matrix and I would like to extract four neighbors of randomly selected entry of a matrix. I have handled if location is not on the boundary. Any suggestion how to handle it ...
1
vote
1answer
94 views

Extract points from given Line[]

As the title says, I have a Line object like this: Line[{{1,2,3},{4,5,6},...,{7,8,9}}] and want to extract certain points. I ...
5
votes
2answers
322 views

Sparse block matrices all wrong

I need to represent $M-\lambda\cdot\textrm{Identity}$ where $M$ is an operator on $V_1\oplus\cdots\oplus V_n$ made from $$ V_1\xrightarrow{M_1}V_2\xrightarrow{M_2}\cdots\xrightarrow{M_{n-1}}V_n\...
2
votes
0answers
38 views

How to extract the same entries from two tables? [closed]

I have 30000 entries in two tables. Now, I want to extract those two entries which are the same. How can I do it? For example, I have two tables, say T1 and T2; ...
2
votes
2answers
192 views

Given a list of linear equations, what is a neat way to use solve on the equations of this list? [closed]

Suppose I have a list of equations, say {2x+b+3c=3, 7x+2b+c=1, x+b+9c=-2} what is a neat way to use Solve[] on that list? ...
3
votes
1answer
39 views

Removing specific entries from a list

I have the list L=8; indx = Range[-π, π, 2 π/L] (* {-π, -((3 π)/4), -(π/2), -(π/4), 0, π/4, π/2, (3 π)/4, π} *) Now I want to delete specific elements of this list,...
1
vote
3answers
56 views

A conditional list generator with stored argument values

I have already made this and the question is really about "how to make this faster and more general (to save the 4 keypresses of D,o,[ and ] that have to be made per-parameter)" The function:...
3
votes
2answers
114 views

Merging pairs of a list with keeping the first elements and adding the second elements

I have a list that was generated by the below code: Do[ Do[ AppendTo[list, {RandomInteger[i], RandomInteger[j]}, {i, 1, 5} ], {j, 1, 5} ] A result can be ...
0
votes
1answer
45 views

Issue with threading matrices

I like this answer, which provides an "autoThread" function for more intelligent threading, but it doesn't work in this example and was hoping for a fix. So for this code: ...

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