Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
7,606
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Is it possible to separate two signals in Mathematica?
I have asignal and I would like to decompose it into two..
this is the datasetTot of both signals
ListPlot[datasetTot, PlotStyle -> {Black, Black}]
I know ...
- 2,997
7
votes
6
answers
317
views
Modify one list according to degeneracies of another
I have two lists, each with four elements, let's say
listA = {0.3, 0.6, 0.6, 0.9}
listB = {0.1, 0.2, 0.3, 0.4}
Notice that the second and third element of ...
- 1,895
3
votes
3
answers
90
views
How to make a table with three columns?
I am trying to make a table with three columns containing the values of p, q and W. I have written the following code which gives multiple columns. I have tried Flattening the table. but I could not ...
- 319
5
votes
4
answers
321
views
Finding the periodicity (or wavelength) in approximately periodic data irregularly sampled
I have irregularly sampled data that looks as in the picture.
Is there a function in Mathematica that allows me to find an approximate or average period or wavelength?
I know beforehand that the data ...
- 567
3
votes
0
answers
91
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Filling the space with rectangles
The problem concerns filling the matrix m x n with rectangles.
...
- 969
15
votes
11
answers
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Fastest way to generate {{a,a},{a,b},{a,c},{b,b},{b,c},{c,c}} from {a,b,c}
What is the fastest way to generate {{a,a},{a,b},{a,c},{b,b},{b,c},{c,c}} from l={a,b,c}? I've tried
...
- 315
1
vote
1
answer
66
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Convert a polynomial to a vector [duplicate]
I am trying to transform a generated polynomial terms into a vector, I used the command 'MonomialList',
...
- 31
1
vote
0
answers
28
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Efficient construction of a formal polynomial using list manipulations
I have a code which is probably extremely inefficient given my inexperience with Mathematica list manipulation. Take as input data:
...
- 1,287
5
votes
1
answer
88
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Abs applied with explicit map not giving same result as built in threading
I was making a code change that required me to change some code that looked like
Abs[list]
to something that looked like
...
2
votes
1
answer
103
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Introduce formal symbols indexed by natural numbers
I'm going to describe a toy example here which I'm hoping with some help, I can then soup up into the more complex application I have in mind.
Suppose the input is a list of lists, and for now take ...
- 1,287
7
votes
6
answers
375
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'Mapping' the values of a list to variable
Suppose I have the variable expr1 = a[n] + b[n], and the list stencil={-1,0,1}. I want to make a function ...
- 937
3
votes
3
answers
138
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Deleting sublists where an element repeats beyond a repetition threshold
I am looking for some help constructing a function Part[M_,N_] which outputs the list of all integer partitions of positive integers up to $M$ such that in each ...
- 1,287
0
votes
1
answer
51
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Create list with integer partitions satisfying some conditions
I want to create a function PartSet[N_,M_] of two positive integer variables which outputs a list of all pairs of integer partitions for all integers up to $M$ ...
- 1,287
2
votes
1
answer
43
views
How to swap multiple values in a large list? [closed]
I have a large list of data points ({{a,b},{c,d},{e,f}...}) that I need to swap the elements of for each point ({{b,a},{d,c},{f,e}....}). This is specifically for a curve-fit, so the data needs to ...
0
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46
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15
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11
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803
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Partitioning a list based on a criterion for sublists
SeedRandom[1];
alist = RandomInteger[{1, 10}, 20]
{2, 5, 1, 8, 1, 1, 9, 7, 1, 5, 2, 9, 6, 2, 2, 2, 4, 3, 2, 7}
I would like to divide this list into sublists (...
- 15k
1
vote
0
answers
30
views
Placing plots around a circle with SectorChart
I need to position some graphs around a circle so that each occupies a sector. There're 18 graphs in total and the first five are shown below:
...
- 1,252
0
votes
0
answers
32
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Show list of points in NDSolve
When I was solving my ODE system with NDSolve, I obtain
{x[t]->InterpolationFunction[{{1., 126.}},<>][t],y[t]->InterpolationFunction[{{1., 126.}},<>][t]}
How can show a list point?
...
5
votes
1
answer
398
views
Why False && {False, False} does not preserve list structure?
I am on Mathematica 12.1.1.0 trying to perform a boolean operation over every element of a list, but preserving the list structure.
When I run
...
- 53
0
votes
0
answers
68
views
Sum of elements products equals to zero
I need to evaluate
$\sum_i a_i b_i=0$, subject to the constraint
$\sum_i a_i=1$.
For the "a" summation being equal to 1, I generated a random list of 10 elements using ...
- 13
11
votes
1
answer
241
views
4
votes
2
answers
338
views
Maps between finite sets
With SageMath, one can do FiniteSetMaps(["a", "b"], [3, 4, 5]) to get all maps from {a,b} to ...
- 315
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votes
1
answer
68
views
Replacement, PatternTest, Module related Question
Let's see how MMA handles following type of expression :
Replace[L, {pattTest1->rhs1, pattTest2->rhs2, pattTest3->rhs3}, {1}]
Specific example :
...
- 2,451
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votes
1
answer
78
views
Classifying elements, by the value of a fixed function, using Replace
Let L be a list of several lists. And the length of each list is less than 1000.
You can create L by
...
- 2,451
4
votes
2
answers
276
views
Sorting a list of "Low", "Medium", "High" into low, medium, high
I have a list with 10.000 entries containing "low", "medium" & "high" data.
It is in random order. How can I sort that to low, medium high?
- 43
0
votes
1
answer
60
views
Create a Table with 3 different variables from 2 Lists and 1 Table
I am new to Mathematica. I learned how to join 2 lists to make (x,y) type of representation using Transpose@{X,Y}. Now my problem is that I have to make a table of 3 variables. I have one set of data ...
- 3
4
votes
4
answers
201
views
Modify list elements if last two entries are equal
Suppose I have a list as follows
{{1, 1, 1, 1, 1, 3}, {1, 1, 3, 4, 1, 1}}
and I want to check the last two coordinates are equal or not. If that is the case then I ...
- 95
1
vote
0
answers
71
views
sometimes Select / sometimes Position is faster
As you see,
For list L,
L1(Select method) is slower than L2(Position method).
But for list <...
- 2,451
1
vote
2
answers
174
views
How to pick lists to satisfy a given form?
I have a list of the following struture:
(my real list also has the same structure, just much longer not just 12)
...
- 1,750
1
vote
3
answers
245
views
How to find the nearest string to another string in a mixed array
I am trying to find which string is nearest to another string in an array of numbers and strings. For example, say I have an array that is as follows
...
- 45
3
votes
3
answers
199
views
Dropping list elements that are members of other lists [closed]
I have a set:
$$A=\{\{1,2,3\},\{1,3,2\},\{2,1,3\},\{2,3,1\},\{3,1,2\},\{3,2,1\}\}$$
I want to drop elements found in sets B and C from A.
$$B=\{\{1,3,2\},\{2,1,3\}\}$$
$$C=\{\{3,1,2\},\{3,2,1\}\}$$
...
- 73
4
votes
2
answers
140
views
Selecting a row from an array by elements of a subset
Assume that
A = Permutations[{1, 2, 3}]
AND $$C=\{1,2\}$$
I want to apply this process
$X=C\subset A$
The output is
$$X=\{1,2,3\},\{2,1,3\}$$
How can the array ...
- 73
0
votes
1
answer
48
views
Find the parameter region where function returns negative value
I have a function $f(m,n)$ where m and n are positive integers. Suppose $f(m,n)$ is like a black box, I can get values of it when I enter values of m and n. I want to scan over a region for example $...
- 51
1
vote
1
answer
40
views
List of ordered pairs from a dataset
I have a dataset with Keys Biz Unit, Rate, Average. Rate and Average are numerical values and I want to pull them from the dataset as a list of ordered pairs without the keys. I've tried various ...
- 81
13
votes
4
answers
590
views
Monitoring Apply / @@@ over large lists
How to monitor and/or print partial progress of Apply, e.g. f @@@ list?
I have found answers using Map (e.g. this nice trick using Echo, or this general trick), but ...
- 233
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0
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45
views
Algorithm: Permutations & Signature
Theoretical side
Simple example: If I have two sets $A_1=\{1,3\} ,A_2=\{2,3\}$
and Permutations[{1, 2, 3}]= $\left(
\begin{array}{ccc}
1 & 2 & 3 \\
1 &...
- 574
0
votes
1
answer
65
views
get positions satisfying multiple criteria
Given a list L.
It is mathematically proven that there is no element in L matching 2 or more patterns in ...
- 2,451
2
votes
3
answers
54
views
How to apply a logical operation to all expressions in a list [closed]
I have a list of expressions and I need to apply AND on all the items.
Input: {xP == 1+x , yP == 3+y}
Desired output: ...
- 351
3
votes
2
answers
234
views
Fast element extraction [closed]
I have a list $A$ of $\sim$ $3.10^6$ complex numbers.
I have another list $B$ of 15000 positions B={1,25,55,100000,...}.
I want to extract the elements from list $...
- 912
2
votes
1
answer
57
views
Displays a few lines on same graph
I've asked a similar question before, but this time I have a slightly more complicated issue.
I have a list of lists, and I want to show a few of the lines in the list.
The following code will plot ...
- 215
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votes
0
answers
66
views
Packed/Unpacked array - what object/like 0 or 1?/how to check/ [duplicate]
In Mathematica, there is a concept called packed array.
...
- 2,451
2
votes
3
answers
139
views
Reducing list of pairs by summing repeating ones
I have a list of pairs $\{\{a_1,A_1\},\ldots\{a_n,A_n\}\}$. Suppose $A_i=A_j$ for some $i\neq j$. Then I would like to eliminate both $\{a_i,A_i\}$ and $\{a_j,A_j\}$ from this list, and instead of ...
- 361
5
votes
1
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118
views
Factor out common terms from a list of terms
I was looking for an automated way to factor out common terms from a list.
Example (assuming n<1):
...
- 973
5
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2
answers
158
views
A Nothing for Associations
In the same way that Nothing disappears from Lists, is there a built-in that when it appears as the value in an association the ...
- 5,334
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1
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52
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A general term of this sequence [closed]
My question is about the set theory.
I have c[0]={{1}} and i want to define c[n] as follows:
...
2
votes
0
answers
39
views
Delete list item if message is thrown
I have a nested list with each element containing FindRoot like this:
{FindRoot[a,b], FindRoot[c,d], FindRoot[e,f],...}
...
- 147
1
vote
2
answers
74
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FindFit; not a valid variable [closed]
I am trying to fit the function in model, however I get
General::ivar: 5000.` is not a valid variable.
this error.
My code is that and
...
- 13
6
votes
5
answers
621
views
0
votes
0
answers
45
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From list shown below - highlight in BOLD the pair with the highest value
I have been trying for sometime to achieve the following:-
Given the list - {{"E", 3}, {"D", 2}, {"S", 2}, {"M", 2}} a list of pairs which maybe 4 pairs - more ...
2
votes
2
answers
238
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