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

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11
votes
3answers
303 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
231 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
75 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
46 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
244 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 ...
2
votes
2answers
91 views

Joining two lists with diverse properties [closed]

I want to make a list from two independent ones. ...
1
vote
1answer
91 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
177 views

Using Cases to get elements in a list

I have the following list: ...
2
votes
1answer
159 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 ...
5
votes
1answer
189 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
94 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
200 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
84 views

How to Increase Performance of Manipulate Recalculating List?

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

Repeating Digits

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

Replacing elements of a nested list by some value

I have a list of list ...
4
votes
5answers
174 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
213 views

Manipulating list of matrices

I have a list of around 100 matrices, that looks like this ...
4
votes
4answers
188 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
181 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
98 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
340 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
179 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
153 views

Cases or Select for catching elements in a list?

I have A list that contains sublists like that: ...
5
votes
4answers
280 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
351 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
118 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
189 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
288 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
152 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
188 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
233 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
98 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
335 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
149 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
632 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
183 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 ...
0
votes
0answers
75 views

Convergence Problem using FindFit

I have the following input where there is a convergence problem in the FindFit as shown in the attached figure.The figure shows 2 plots: one of the real data and the other of the fitted line. Any ...
0
votes
0answers
67 views

list numbering problem

I have a list that is generated from a unparsed matrix, and another list that is generated by a parsed matrix. However, since the second one is parsed, the numbering of the elements in the list have ...
2
votes
2answers
58 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 ...
5
votes
3answers
291 views

Element-wise list operation on list of lists [closed]

Suppose a function F operates on list A: $$A=\{a_1, a_2,\cdots, a_n\}$$ I have a list of lists, B: $$B=\{A_1, A_2,\cdots,A_m\}$$ Is there a syntax to specify that F should operate on members of B, ...
3
votes
2answers
54 views

Read off entries of UndirectedEdge [closed]

Suppose I have an undirected edge e=UndirectedEdge[a,b]. How do I extract one of the entries a,b of e? I tried accessing e like a list, but that didn't work (...
8
votes
2answers
196 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
150 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
149 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
204 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
305 views

One to Many Lists Merge

I have two lists: ...
2
votes
1answer
72 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
71 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
148 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
83 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: ...