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

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11
votes
3answers
341 views

What is the best way to flatten a linked list with lists as values?

By following the advice on this site I have ended up with a linked list like the following: acc = {{1, 2}, {{2, 3}, {{3, 4}, {{4, 5}, {{5, 6}, {}}}}}}; This was ...
4
votes
5answers
248 views

Extracting Coefficients from a List of Sines

I want to extract the coefficients from the following list: list={16.2219 Sin[16.2219 t], 6.60924 Sin[6.60924 t], 13.927 Sin[ 13.927 t], 2.91309 Sin[2.91309 t]} ...
1
vote
1answer
79 views

Transforming a nested list for textual output

Hello I have a data structure based on lists, with items, subitems and subsubitems, and I want to display a textual output with a description. ...
0
votes
2answers
61 views

How do I generate a list of delayed rules? [duplicate]

I want a list like this: {x :> Print[1], x :> Print[2], x :> Print[3], x :> Print[4], x :> Print[5]} I tried: ...
6
votes
2answers
253 views

List of tuples without forbidden pair

How do you get a list of tuples in Mathematica that do not include certain pairs of elements? For example, I'm trying to list sequences of matrices of a certain length, and I do not want two adjacent ...
1
vote
1answer
106 views

Manipulate filters in arrayplot with graphical user interface

I have a set of images which need to be filtered by different filters. So I have made an interface in which the user can choose his or her filter. However I now want to manipulate the degree of the ...
4
votes
4answers
181 views

Using Cases to get elements in a list

I have the following list: ...
2
votes
1answer
237 views

Sort eigenvectors of a list of matrices

I have a list of matrices and want to obtain a list of eigenvectors and eigenvalues for each matrix, both sorted by the size of the eigenvalue. If I write ...
12
votes
7answers
475 views

Product of elements of a list

Sum is for functions; Total is for a list. Product is for a function; what is the command ...
6
votes
1answer
226 views

Conditional string replacement

I have a list of text and need to replace an element based on the text that appears in the element before it. Example of my list: ...
0
votes
0answers
101 views

Solution of a set of quadratic congruences (Chinese remainder)

Edit: Please remove this question. I think there are mathematics error in what I am asking. You are welcome to edit the question if you can state the problem correctly. I have a set of quadratic ...
5
votes
4answers
224 views

Signed power set of a list

Given {a, b, c, ...} with $n$ elements generate a list with $2^n$ elements. For example, if the list were {a, b, c}, then the ...
1
vote
1answer
94 views

How to Increase Performance of Manipulate Recalculating List?

I have a list in the form of prices below. ...
9
votes
5answers
420 views

Repeating Digits

I have written ...
5
votes
6answers
380 views

Replacing elements of a nested list by some value

I have a list of list ...
4
votes
5answers
185 views

Counting the number of instances where items at the same position in two matrices are equal?

Given two matrices having the same dimensions: m1 = {{1, a, 2}, {4, 5, 0}, {g, a, d}} m2 = {{1, b, 2}, {7, 2, 0}, {a, a, a}} Is there a built-in function that ...
3
votes
1answer
310 views

Manipulating list of matrices

I have a list of around 100 matrices, that looks like this ...
4
votes
4answers
229 views

Sublist pattern matching

Is there any way to simplify the following pattern: {p___, {a___, x_, x_, b___}, q___} :> {p, {a, x, b}, q} Ie. where I remove duplicated elements within ...
5
votes
4answers
216 views

Finding the position of a single array in a list of arrays that contains wildcard variables

Consider two lists: superList = {{wc,wc,1,wc,wc}, {wc, wc,2, wc, wc}, {wc, wc, 3, wc, wc}, {wc, wc, 4, wc, wc}}; littleList = {a,b,3,c,25}; In ...
3
votes
2answers
107 views

The conflated two uses of SameTest within Intersection

Intersection works as expected in this case... a = Range[1,5];b=Range[3,7]; Intersection[a,b] giving... {3,4,5} However if ...
6
votes
6answers
357 views

Total by a criteria

I am developing a weighted KNN algorithm. In a step, I need to do the sum of weights of each class. For example: ...
4
votes
2answers
202 views

Looping through a list partition

I got the following list and I would like to loop and partition this list in the following way. ...
3
votes
3answers
167 views

Cases or Select for catching elements in a list?

I have A list that contains sublists like that: ...
6
votes
4answers
316 views

Pattern matching - comparing two lists

I would like to compare two different lists to see if the shorter one is a member of the larger e.g. is the list {2,3}, with that sequence of elements, a member of {1,2,3,4,5}? I have tried using ...
13
votes
2answers
361 views

Bad performance of LengthWhile?

A friend of mine showed me this example, it's a test comparing LengthWhile to a self-made lengthwhile written in a direct and ...
3
votes
2answers
126 views

Partition a list dependent on consecutive list values

I have a list of 2D points which I partition every time the distance between consecutive list elements is bigger than a certain threshold. In a second step I select all the lists that start within a ...
8
votes
2answers
208 views

Bad performance from SubsetQ?

Can I say this is a bad performance from the new V10 function SubsetQ? Here are some tests comparing it to ...
6
votes
3answers
319 views

List Manipulation on Array with subscript elements

I am trying to write a function which operates on an array with subscripted elements. As an example i have the array a={$1_3$,$2_2$,$4_1$}, which means i have 3 amounts of value 1, 2 amounts of value ...
3
votes
2answers
176 views

Convert matrix rows into variables

Can anyone show me how to set all matrix rows to variables. For example, I have matrix w={{1,2,3},{3,2,1},{0,0,0}} and I need to set each matrix row to be separate ...
1
vote
1answer
223 views

Find maxima and minima of data like {time,value}

I have a list of time and values of the charge and discharge of a capacitor, and i want to separate in two list of {time,value of charge} , {time, value of discharge} I know there is a lot of the ...
2
votes
4answers
237 views

Get 'new' list of data by manipulation 'old' list

Assume I have the the following list of data: valuesOld = {5, 10, 15, 20, 25, 35, 40, 45, 55, 65, 80}; I would like to construct the following list: ...
2
votes
3answers
114 views

Remove all “not equal” clauses from an expression

I am banging my head against the following question: how can I have Mathematica take cond = 2 a >= 3 b && 70 a >= 19 && 20 a != 13; and ...
3
votes
3answers
361 views

Faster Integer Approximation of pi

I'd like to speed up this calculation: First[Sort[Table[{k,Abs[Round[k/Pi]Pi - k]1.{k,1,100000}],#1[[2]]<#2[[2]] &]] The code above generates a list of ...
5
votes
5answers
153 views

getting at the right parts of a list

I have a way to solve my problem, but it seems like there should be something better. Also I realize that I probably don't have a good enough handle on how to get at parts of lists the way I need to. ...
14
votes
12answers
659 views

Join lists with nested list

Is there a way of smarter way of joining list of the form l1 = {a,{b,c}}; l2 = {d,{e,f}}; l3 = {g,{h,i}}; To obtain ...
6
votes
3answers
212 views

Remove Successive Duplicate From A Large List (200k by 4 matrix)

I am interested in removing successive duplicate rows from a very large list (~200k rows by 4 columns) using Mathematica.The built-in 'DeleteDuplicates' seems to remove all duplicates, I am interested ...
2
votes
2answers
64 views

parsing a list or vector

I have a table of elements that generate a list q[i_]=i; B=Table[q[i],{i,1,50}] I would like to parse the list meaning, take the first 10 elements, then take ...
9
votes
2answers
217 views

How to partition a list according to a value in the list

I have a list of the form $\{\{d_1,c_1\},\{d_2,c_2\},\ldots,\{d_n,c_n\}\}$. The values c_i take values between $1,\ldots,k$. I want to partition the data into $k$ lists according to the values $c_i$. ...
5
votes
2answers
164 views

Sorting out atom types in an XYZ file

I am trying to rewrite the output of "VertexCoordinates" such that instead of a hybrid list of atoms and coordinates that result from using the following input program, I want all coordinates of the ...
3
votes
3answers
176 views

Working with calculations that depend on the previous value in a list

I'm trying to make calculations on a list that depend on the previous value. In my case I'm doing event detection - detecting the point where a value rises above some threshold for the first time ...
5
votes
2answers
225 views

How to define even permutations correctly?

I define even permutations as following, but there may be some error. I use it in two different way and get different output. ...
6
votes
6answers
325 views

One to Many Lists Merge

I have two lists: ...
0
votes
1answer
147 views

Rearranging 5 equations

I am trying to rearrange 5 equations in terms of 5 variables. I have the equations for y1, y2, ...
2
votes
1answer
76 views

Compare some lists, if elements are almost equal

I've got the solutions of three systems on two variables (a and b) that gives results sometimes almost equal. The three list are not of equal length! For example: ...
3
votes
1answer
87 views

How can I create a set (list) provide a kind of rule/algorithm?

Example: S = {r ∈ Q : r² < 2} Let S be the set of all rational numbers whose squares are less than 2. It follows that 1 ∈ S, 4/3 ∈ S, but 3/2 doesn't ∈ S because 9/4 ≥ 2. Thank you.
2
votes
3answers
158 views

How to multiply specific columns in a matrix of data?

So I need to make a plot of some ~2000 data points I have from a spreadsheet. I'm able to import the data just fine, it stores it like so sundat ...
3
votes
1answer
89 views

Remove values from list element, and add to other element

Basically what I need is to make a list of 400 elements, all have value 1. The next step is to create a function, that subtracts value (-1) from an element, and adds that to another element. So: ...
1
vote
1answer
98 views

How to understand the extensional usage of Flatten? [duplicate]

Recently, I have been reading Mathematica program that written by many advanced Mathematica user, like Mr.Wizard, J.M., Kuba,etc to improve my programming capacity In the On generalizing Partition[] ...
9
votes
5answers
715 views

Coalition Games

Suppose an election produces the following result: result = {{"a", 120}, {"b", 80}, {"c", 50}, {"d", 30}}; Letters are parties and numbers seats. To form a ...
5
votes
3answers
943 views

Generating random symmetric matrix

Suppose first that I want to generate a matrix whose elements are independent and identically distributed (i.i.d.) with distribution dist. This is easy: ...