Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
6,863
questions
0
votes
1answer
43 views
How to apply color gradient in listplot based on the density of points
I have a list of points ( a list with sub lists which are {x,y} coordinates. I would like to have a listplot where the areas with higher density of points are in darker colors and areas with lower ...
1
vote
0answers
39 views
Using the Line command with a bound on distance between points
Suppose I use the Line command applied to a list (or more accurately apply Graphics[Line[list]] or ...
7
votes
3answers
289 views
ReplaceAll, Unexpected output
Each week I import a dataset, and every week the dataset differs in length (the number of records). After the import I need to do some transformations. One of these transformations is the ReplaceAll.
...
5
votes
2answers
320 views
Summing over Partitions
Imagine I have a list of integers $l=\{l_1,l_2,...,l_{50}\}$, say, for example
l = RandomInteger[10, 50]
and I want to find how many ways there are of summing ...
9
votes
2answers
221 views
1
vote
2answers
48 views
Is there a workaround to dereference a list element that's the name of an undefined symbol, and iteratively assign values to the symbols in the list?
The title mostly covers what I would like to do. The image below shows in some situations it is possible dereference an element in a list using Evaluate to assign a value:
...
1
vote
1answer
36 views
How to check if a complex number belongs to a quadratic field
I am working with lists of complex numbers and want to be able to determine which out of these lists contains only elements from a certain quadratic field, $\mathbb{Q}(\sqrt D) = \{ a+b\sqrt D :a,b \...
2
votes
1answer
104 views
0
votes
3answers
77 views
ReplaceAll in list not working as expected [closed]
This is my code.
lst = {1, 3, 5};
ReplaceAll[lst, lst[[2]] -> {7, 9, 11}];
lst
It is supposed to get output ...
1
vote
4answers
150 views
How would we extract elements of a list greater than a certain value? [closed]
Say we have a list
{35,210,67,950,32,365}
how would we extract all the elements greater than 100 from this list (using a function)? The desired output would be ...
7
votes
2answers
183 views
Find All Permutations for Multiset
Take a list with repetitions, say {a, a, b, c}, and some permutation thereof, say {c, a, b, a}. I want to know which ...
asked Nov 5 '20 at 17:55
AccidentalFourierTransform
9,0421 gold badge15 silver badges48 bronze badges
0
votes
3answers
123 views
How to do two different kinds of binning for a given list of elements?
I have a long list consists of float numbers with some of them duplicated as shown below.
I want to divide this list into bins;
with equal bin width so that in each bin there might be one or more ...
1
vote
1answer
63 views
How to sort the list A in an increasing order, such that I can modify the other list B with change in element position of list A
I have two lists A and B, I am trying to change modify the elements of list A in an increasing order such that my list B should also be changed according to list A. The node no list is given below.
<...
0
votes
3answers
54 views
Manipulating a list while maintaining the nested list structure
Suppose I have a list of pairs of complex numbers with nesting as follows
...
0
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0answers
44 views
Solving equations using lists of data
I have a list of pairs of numbers that represent empirical data for U(n) e.g. {{n1,U1}, {n2,U2},...}.
Is there a way to use this discrete data set to solve something along the lines of:
...
1
vote
1answer
99 views
How can I find different areas of triangles from a list of points?
If I have a list of points such as {{1, 1}, {4, 7}, {24, 67}, ..., {17, 83}}, how can I find the area of triangles formed by different combinations of these points? ...
1
vote
2answers
176 views
Converting a list to an array
Let's assume that I have a list that I can access like list[[i, j]]
How can I convert it to an array such that:
...
1
vote
1answer
76 views
When a list is not a list
When I provide a list of local variables to Module, it complains that it is not a list:
v = {x, y};
Module[v, x = 2]
... Module: Local variable specification v is not a List.
So my question is how do ...
6
votes
2answers
121 views
Split in non-overlapping sub-lists with elements within an interval from the first member
I want to split a large ordered list into consecutive non-overlapping sub-lists, such that all elements are within an interval from the first member of the sub-list . For example:
...
0
votes
1answer
82 views
Mathematica refuses to distribute a scalar through parentheses
Iām working on a problem involving Kelvin-Helmholtz instability and Iām trying to perform the linearization on Mathematica. For some reason when I get to my first order equation (Īµ Ć stuff + O(ĪµĀ²) == ...
1
vote
2answers
37 views
What does problem statement mean by “using the Table function”? [closed]
Can you help me on the following question?
Generate the list
{{0}, {0, 2}, {0, 2, 4}, {0, 2, 4, 6}, {0, 2, 4, 6, 8}}
using the ...
7
votes
2answers
252 views
How to select the fastest approach for large numerical data computations?
I really love the flexibility of Mathematica: there are several ways to perform one task. However, to get the performance of the intense numeric calculation, it can ...
0
votes
1answer
30 views
Displaying only one component of the list [closed]
I wrote a code which gives me a list which has one coordinate point (for example {{10,11}})
I was wondering how i can only take the y part (which is 11)
I tried using:
...
2
votes
2answers
106 views
Using iterative functions to specifically sort a list
The following code sort the list li in a such way that consecutive terms $t_n,t_{n+1}$ are of the from ...{x_,y_}, {y_,z_}.... i....
2
votes
1answer
61 views
Substituting Atoms in .XYZ File
I have a crystal structure in which I'd like to randomize the placement of cations from an initial structure. I have a .xyz file (given here https://pastebin.com/d5UcNr2h) which gives atomic ...
1
vote
0answers
43 views
How to get list[[i,j]] from a list {i,j} [closed]
My problem is more complicated than what follows but this is the minimal working example.
Lets say I have:
l1={1,2}
I have a list:
...
2
votes
3answers
36 views
Select element in a multidimension list containing one element
Imagine that I have a list like:
list={{{{1}}}}
To access the number 1, I could do list[[1]][[1]][[1]][[1]]
Of course it is very ugly but this is how I would do it ...
0
votes
0answers
36 views
Using ListDenistyPlot to Plot 3 Dimensional List
I have a question regarding how to use ListDenistyPlot.
I am trying to plot a large list of data (150,000 data points) by using ...
3
votes
1answer
99 views
function over list mathematica
I work on problem that need to define function with two list of data as follow
...
0
votes
1answer
60 views
Generating a list of outputs using For[] Loop
I have a question regarding the use of the For[] loop to generate a list of outputs from a function that generates random outputs. Essentially, creating a sample of ...
5
votes
2answers
126 views
Modify each element depending on previous elements
I'm looking to see if there's a more idiomatic/concise/neat solution than what I have for this.
I have a list of boxes with heights and I want to stack them; that is, add to each box the distance to ...
2
votes
1answer
49 views
Replacing $x,y$ in $f(x,y,z)$ with values from a list
I'm sure there is a simple solution to this using map or apply, but its not occurring to me.
Suppose I have a function $f(x,y,z)= x+y+z)$
And I want to evaluate $f(x,y,1)$ for $\{x,y\} ā \{\{1,2\},\{3,...
1
vote
1answer
69 views
4
votes
2answers
100 views
Finding strings which contain a given substring
Using the following commands (which may be inefficient) I can generate all words of length $j$ on the alphabet $\{0,1\}$:
sd[st_]:=StringDelete[st, " "]
<...
0
votes
2answers
69 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
30 views
Selecting parts of 2d array based on x value
Given a 2d array such as x={{1,2},{2,3},{3,4},{4,5},{5,6}} how would I extract all pairs where the first value is between 2 and 4 such that ...
1
vote
1answer
92 views
Optimizing a slow For loop
I know that this is a "beginner question", and, in fact, I am. I want to improve my code, as it takes really too much time to run.
I have already read some other discussions, like here,
but ...
1
vote
1answer
46 views
Getting columns (instead of rows) using Reap/Sow
In my program, I'm computing a vector inside a Do loop. The example below is an overly-simplified version, but the structure is the same (the original code can't be ...
0
votes
1answer
42 views
Do or For cycle to have more than ListLinePlot
I have a generic function:
f[a_,b_]:=Module[{e,f,g,h}]
which returns the scalar g and the list ...
7
votes
5answers
685 views
2
votes
2answers
68 views
Sorting a list of pairs so that the larger number in the pair appears first [closed]
Imagine I have this data.
I want to sort it so that it takes the form:
{{<larger>, <smaller>}, {<larger>, <smaller>}, ...},
Any help ...
0
votes
1answer
33 views
Assume symmetric F[a,b] = F[b,a] when CountDistinct and similar functions
I wonder how I can tell Mathematica to regard the following expressions: F[a,b] and F[b,a] as being equal, so for example ...
3
votes
2answers
74 views
Join sublists on condition
I have a nested list of integers and want to join any sublist matching a condition to its left neighbouring sublist, iteratively. Conveniently, the joining condition is whether the length of the list ...
0
votes
0answers
47 views
Long execution time using position
I have two lists, for example:
List1={2,4,6,8,10,12}
List2={4,10,12}
I want to find the positions in List1 such that the element at that position is equal to the ...
0
votes
1answer
37 views
Using and Naming different sets of data in a manipulated chart/plot
I am trying to visualize advertisement data from amazon which is comprised of a dozen or so campaigns, each of which has three subgroups and each subgroup has its own performance data (metrics). ...
0
votes
1answer
47 views
Performing mathematical operation on the y coordinates in a list of coordinates
I have a list that contains a set of coordinates in the form {{x1,y1}, {x2,y2}, ...}. I want to edit the list in manner that it takes the log() of all the y coordinates only. Essentially, I want ...
3
votes
1answer
68 views
selective deletion of list members
I have a list and need to remove certain members of the list.
lis = {f1,a,b,c,d,f2,e,g,h,i,f1,j,k,l,m,f2,n,o}
I need to remove each occurrence of f1 and the ...
0
votes
1answer
22 views
How to store outputs as coordinates and use ListPlot to plot them?
so I have a program that outputs a desired value for incrementing values of alpha. Right now, my program prints a list of these for 40 values of alpha in the form {alpha, newValue}.
...
0
votes
2answers
57 views
Using Table to iterate over two lists element by element instead of as a matrix
So I have two lists generated in the following fashion, I don't know if it's the most efficent way to get these, but that's beside the point right now.
...
0
votes
0answers
65 views
Why does Log[Abs[#]] return a complex number?
For a nonzero number $x$, $\log|x|$ should be a real number. Why does the following NestList contain non-real numbers when no numbers involved are close to zero? Is it a bug?
...
