Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
9,397
questions
1
vote
1
answer
61
views
Creating coefficient matrix
Suppose I have 3 elements, $\{A1,A2,A3\}$. I have 3 independent polynomials, stored in a list $\{A1-s*A2,A2,A2+A3\}$. I want to create a matrix form which will help to visualize easily which elements ...
3
votes
1
answer
149
views
Why is the code with multiple Do slower than the one without them, and why is For faster than Do?
For some table tab having N rows and n columns, I need to go over all its rows $j$ and ...
0
votes
0
answers
45
views
How to flatten a list in NMaximize?
I have the following function:
...
3
votes
1
answer
118
views
FindPeaks in a 2d list and half values
FindPeaks is a nice little help. But it only works on 1D lists and tends to return half integer values for positions of the peaks which are ultimately very useless ...
5
votes
2
answers
154
views
Numerical integration of a list
I have a list, p, obtained by a complex numerical procedure. Its element has the structure: {k,fi,z}. Below I give a simplified ...
7
votes
7
answers
401
views
Add the number of occurrences to the list elements
I'm not explaining it well, sorry.
There is a list[j] consisting of randomly selected number {a,b} elements.
For example,({j,4})
...
0
votes
0
answers
101
views
Why is the following code not compilable?
The code below should replace particular elements of some table acccolumns if some condition is satisfied:
...
0
votes
1
answer
60
views
Why does the following code not change the table?
Consider the following code:
...
7
votes
5
answers
158
views
Generating all expressions of the form $a*x + b*y + c*z$ where $a,b,c\in \{ -1,0,1\}$
Suppose I have an expressions, i.e.,
a*x + b*y + c*z
If the coefficient $a,b,c \in \{-1,0,1\}$, I want to make them as a list., i.e. ,
$\{ \{-x+y\},\{-x-y-z\}, \...
4
votes
1
answer
81
views
ListPlot color function depending on point stability
I have the following code that finds the critical points of the function enAll[v1,vTotal] and there is a plot of those points as shown below. However, I need each point on the plot to be colored ...
1
vote
2
answers
80
views
Changing part of a list of unequal arrays
I have {x, y, f(x,y)} data in multiple (n x 3) arrays with unequal length, which I read in from different files in order to later plot them using ListPlot3D. I ...
4
votes
2
answers
215
views
Efficient use of GatherBy on large list to remove duplicates
I have a large nested list of rules, wherein elements which have repeated entries on the LHS of the rules should be deleted. For instance
...
4
votes
2
answers
152
views
How to re-arrange a list of results?
The function mat[v1,vTot] has either one solution or three solution, depending on what vTot is. I want to make a table with pairs of points corresponding to the value of mat and its corresponding vTot....
6
votes
3
answers
419
views
How to combine elements of a list who have two elements in common?
I am a bit new to both Mathematica and StackExchange, so I apologize if I have made any mistakes in my question or missed an obvious answer.
I have lists of the form
...
4
votes
2
answers
129
views
Remove outermost curly brackets for table of variable dimension [duplicate]
I have $\vec k=(k_1,k_2,...,k_d)$, where $d$ is variable. I want to construct a table that iterates $a_i$ from $0$ to $k_i$, over a function of $\vec k$ and $\vec a$. Here is what I did (here $k$ will ...
1
vote
1
answer
48
views
How to obtain a list of pairs of exponents in a double series expansion?
Let's say we have a function of two variables $f(x,y)$ and we work out its Taylor expansion up to some power. I would like to use Mathematica to construct a list of all exponents that appear in the ...
2
votes
0
answers
62
views
Pick position of a particular list in the list of lists [closed]
Suppose I have some following lists with different size
...
0
votes
1
answer
273
views
Why are the results of these codes different?
I apologize for the very long question with a relatively complicated code. I am dealing with a real problem, and the question below appeared from my attempt to simplify this problem to ask about it ...
1
vote
2
answers
102
views
How to make a list be skipped if it is an empty set when it is being iterated over
Could you give me some advice?
There is a box[a,b] in which the number and number of lists are randomly generated.
For example as follows.
...
0
votes
1
answer
64
views
Code doesn't stop running - how to fix Part::partw? [closed]
I have this code divided into two notebooks, the first notebook is running just fine, and It gives some information that the second notebook uses, like some variables. The second notebook exhibits the ...
3
votes
2
answers
102
views
Create a new table by deleting some similar rows, provided that their outputs are collected
How to delete duplicate rows, collect their outputs in general, and create a new table.
The figure below shows the idea required to create the new table
The idea is that if the rows are similar in ...
4
votes
2
answers
123
views
Selecting sublists from a ragged array of lists of strings
A ragged array of strings with a mix of sublists is processed to output some sublists and not others.
The sublists to output have a date, data, and information; in no particular order.
The information ...
0
votes
1
answer
50
views
Use table data to substitute into a function
If I have the following function
Rx = Subscript[x, 1] Subscript[x, 2] + Subscript[x, 3] - Subscript[x, 1] Subscript[x, 2] Subscript[x, 3]
I want to add it as a ...
2
votes
1
answer
54
views
Collect columns in a table
How can I add the elements of certain rows and show them as a new row in the table?
The following table shows the required process:
My attempt is just to make the table
...
6
votes
3
answers
287
views
Split list into ascending sublists
I would like to split a list into non-overlapping, ascending (more precisely, non-descending with ≤) sublists. The function would be close to LongestOrderedSequence,...
4
votes
4
answers
221
views
How to regroup elements of a cluster?
Given a clustering of unique elements,
clustering = {{10, 40, 30}, {200, 500}, {6}, {7}, {8}};
How do I group a given subset of them into the same cluster?
eg:
<...
5
votes
9
answers
386
views
Rotate elements in a list using a for loop
I have the following list.
data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
I want to replace (rotate) each element using a for loop. In the first step, the first element ...
0
votes
0
answers
61
views
How can I tell Mathematica that $0^0$ is equal to 1 [duplicate]
I input: Table[Binomial[3, k] (3 - k)^(3 - k) (k + 1)^(k - 1), {k, 0, 3}].
Mathematica returns: {27, 12, 9, Indeterminate}.
I want Mathematica to return: {27, 12, 9, 16}.
1
vote
1
answer
123
views
Fixing code for a combinatorics problem
The problem I am solving is:
Determine all possible values of positive integer $n$, such that there are $n$ different $3$-element subsets $A_1,A_2,...,A_n$ of the set $\{1,2,...,n\}$, with $|A_i \cap ...
5
votes
2
answers
354
views
Efficient way for writing -1 <= X[i,j] <=1
I have an $m \times n$ variable $X$. I want to write the following constraint
...
3
votes
1
answer
90
views
Constructing Toeplitz Matrix
How can I construct this matrix?
5
votes
3
answers
204
views
How can I remove and keep the elements of this set?
I have a list
list = {{1, 3, 7, 1, 2, 1, 4, 7}, {6, 2, 7, 9, 4, 3, 6, 7}, {2, 8, 8, 2, 3, 2, 4, 6}, {5, 7, 7, 5, 2, 1, 2, 4}, {8, 10, 10, 8, 2, 1, 2, 4}}
Consider ...
2
votes
2
answers
74
views
Error with using ReplaceAll
I wrote a For Loop. In this For Loop, I want to change the values of a list. The main issue is:
I have a nested list like:
...
3
votes
4
answers
210
views
Build a region from an unsorted set of points (Imported from a .DXF file)
Please consider trying to download the following .dxf files :
DXF File - HEA
DXF File - UNP
DXF File - RRW
Context :
Every file contains a drawing of a particular type of steel profile used in civil ...
1
vote
1
answer
39
views
Evaluate integrals on imported data and export the results
I have imported an excel file Data=Import["data.xlsx"] which gives the output like this:
...
4
votes
3
answers
211
views
Find shortest subsequence
We will deal with arrays of chars, but not strings!
Let we have the next three arrays:
...
8
votes
3
answers
473
views
How to set to 0 all terms in a matrix which contain a minus
For a matrix like
F = {{β , x β}, {-2 β, -3 β}};
F // MatrixForm
I would like to set to 0 all terms which contain a minus, in this case the bottom row, getting
<...
2
votes
3
answers
305
views
How to plot properly the following data?
Consider the following test data:
...
1
vote
2
answers
125
views
How could the whole series of graphics be saved?
I would like to save a series of graphics of a function as pictures. But the problem is that I can't manipulate the name of the graphs, because of that only the last graphics in the series is saved.
...
4
votes
2
answers
88
views
PositionIndex of isomorphic value
The following example is a simplified version of a problem I am working on:
equivalent[x_, y_] := Mod[x, 7] == Mod[y, 7]
Given a list, say {3, 7, 5} and an integer ...
9
votes
4
answers
2k
views
Find Roman numerals up to 100 that do not contain “I"
The question is from Elementary Introduction to the Wolfram Language, section 28 Tests and Conditionals: Find Roman numerals up to 100 that do not contain “I”.
What am I doing wrong that the following ...
1
vote
1
answer
127
views
How to get DFT from Sound/Audio/Image?
When I'm trying to do Discrete Fourier Transform or just get a ListPlot of values from Sound object, I get error message..
I understand that Fourier command (and ListPlot of course) works only with ...
1
vote
1
answer
105
views
How to sort eigenvalues (from minimum to maximum) and their corresponding eigenvectors?
When using NDEigensystem, the first eigenvalue corresponds to the first eigenvector, the second eigenvalue to the second eigenvectors, and so on. I would like to sort the eigenvalues from min to max, ...
0
votes
2
answers
92
views
Multiplying a certain column from a table with a function
I have the following list of matrices whose second entry I would like to multiply/divide with a function, say f, and store the resulting table as a new table. How should I go about doing that? Thanks
*...
1
vote
0
answers
75
views
Separate the elements of a row [closed]
I have a $\psi$:
{a,b,c,d,e,...}
for example for 10 letters. How can I change it in the format:
{{a},{b},{c},{d},{e},...}
I ...
1
vote
1
answer
149
views
How to combine Flatten and Partition? [closed]
In order to get list x4 from list x1, I used three operations. How to get list x4 in one ...
1
vote
3
answers
99
views
List manipulation and plotting
I have a code which takes as input RandomSample[Range[d^2],4] for a given d and outputs a value ...
3
votes
3
answers
241
views
How to join two one dimension lists as columns in a matrix [duplicate]
I would like to take a one dimensional list, e.g., list1={1,2,3} and add a second column, e.g., list2={a,b,c} to get ...
3
votes
2
answers
148
views
Plotting two variables from multiple lists
Given a few lists as below
...
2
votes
1
answer
62
views
comparing lists of unequal lenghts
Suppose I have three (nested) lists A , B and Cmat where ...