Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
9,315
questions
4
votes
3
answers
208
views
Find shortest subsequence
We will deal with arrays of chars, but not strings!
Let we have the next three arrays:
...
- 1,085
8
votes
3
answers
471
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
<...
- 1,582
2
votes
3
answers
305
views
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.
...
- 1,731
4
votes
2
answers
86
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 ...
- 1,596
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 ...
- 417
1
vote
1
answer
117
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 ...
- 21
1
vote
1
answer
99
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, ...
- 1,731
0
votes
2
answers
90
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
*...
- 31
1
vote
0
answers
74
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 ...
- 1,493
1
vote
1
answer
148
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 ...
- 1,731
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 ...
- 376
3
votes
3
answers
220
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 ...
- 131
3
votes
2
answers
133
views
2
votes
1
answer
61
views
1
vote
2
answers
75
views
How do I find the "edge" values/positions in a list?
I have a list of values and am interested in finding the contiguous region above a certain threshold.
I have gotten this far,but cannot seem to find the correct way to find the edges. Note: It is not ...
- 321
1
vote
1
answer
64
views
How to define the boundary of the 2D region outside of the list of sub-regions?
Consider the following file. It includes a list of tables defining some regions.
...
- 4,984
1
vote
1
answer
152
views
4
votes
2
answers
185
views
Finding the sum of eigenvalues of a matrix depending on the parameters
There is a system that has the following Hamiltonian: $H=-\frac{1}{2}\Delta-\frac{1}{r}+\frac{B^2}{8}\rho^2-\frac{B}{2} (m + 2 m_s)$, where $r=(\rho,z,\phi), B=5, m=0, m_s=-1/2$. To find the ...
- 1,731
5
votes
5
answers
329
views
Evaluate a function with two lists and table
I have the following function:
f[x_,y_]:=x^2/y
and two sample lists (that are actually longer):
x={2,4,6}
y={3,5,7}
I want to ...
- 153
1
vote
2
answers
97
views
Generate family of linear inequalities from vector variable for use in `FindInstance`
Suppose that I have a vector variable xvec = Array[x, 10].
How do I generate the family of linear inequalities
$$F = \{ {x\in\mathbb{R}^{10}:x_1\geq x_2,\ldots,x_9\...
- 125
0
votes
1
answer
25
views
sum elements (variables) of a vector variable [closed]
I would like to sum elements of a vector variable, e.g.,
Is
xvec = Array[x, 10]
s24 = Sum[xvec[i], {i, 2, 4}]
where $s_{24}:=\sum_{i=2}^4 x_i$.
However, I am ...
- 125
1
vote
1
answer
73
views
0
votes
1
answer
107
views
How to split the table with different number of columns into those with equal number of columns? [closed]
Consider the following table:
tab = Join[RandomReal[{0, 1}, {2, 2}], RandomReal[{0, 1}, {3, 4}],
RandomReal[{0, 1}, {2, 3}]]
Could you please tell me how to ...
- 4,984
4
votes
4
answers
272
views
2
votes
2
answers
287
views
Is there a Mathematica function that puts a list of numbers in a normalized [1, 10[ scale
I have the following list:
...
2
votes
3
answers
166
views
How to write a function in the following form f[a_, b_, c_,...] so that it is flexible with respect to the number of arguments?
@lericr have written under several of my questions that the way I try to modernize the code could be made much simpler. Below is the original part of the code. The remaining parts have similar designs,...
- 1,731
7
votes
11
answers
454
views
How can I change the data arrangement in a list?
I have data that, when imported to my notebook, is shown in the form:
list = {{1,2,3},{4,5,6},{7,8,9},{10,11,12}}
I want to transform this into:
...
- 73
2
votes
1
answer
85
views
How to correctly reassign variables {c11 -> p11, c12 -> p12} using a Table or some other similar structure?
Why is the value of the function Pxx[1,2] is a number but the function Pxxx[1,2] is an expression? Isn't this construction ...
- 1,731
2
votes
2
answers
81
views
How to use sequence of variables (Sequence) correctly?
Why does the function EER[1,2] have a different value than the function EERR[1,2]? Isn't the entry ...
- 1,731
2
votes
2
answers
75
views
The correct notation of a function that contains an expression with NIntegrate
I tried to set the function Px[a1_, b1_, qa_, qb_]. Why does Px[1.22, 0.44, 1.40, 1.81] not give out a specific number?
...
- 1,731
2
votes
1
answer
41
views
Table with an angle | rotate the co-ordintae
I have the following,
Flatten[MapAt[Reverse, 2]@
Table[{i, j}, {i, 0, 10, 10}, {j, 0, 90, 90}], 1]
that gives,
...
- 811
9
votes
7
answers
759
views
How to quickly make a rectangular array of continous 1 and 0 given the start position of 1
I would like to make a rectangular array of 1 and 0 with continuous columns of 1.
We are ...
9
votes
4
answers
602
views
Check if a string is a date
I have a list of strings,
{"BD4675365", "Corp", "Managers", "Syndicate", "2021-03-08", "8434926"}
and I ...
- 1,937
0
votes
1
answer
35
views
saving output and ListPlot the output:
Let's say I have
x = 1; y = 2;
d = x^2 + y^5 ;
and
x = 5; y = 3;
d = x^2 + y^5 ;
and
...
- 811
1
vote
0
answers
60
views
get the first from a list using slots [closed]
Problem. I work with a list and want to get the first element. For specific reasons I want to use # in combination with Map
For example
...
- 2,585
2
votes
1
answer
49
views
How to select only particular values from the list using dialog windows?
Consider some list:
list = {"A","B","C","D"}
How to select only particular values from it using a dynamic dialog window ...
- 4,984
0
votes
1
answer
67
views
3D plot not working, find max/min points [closed]
Im trying to plot this graph in mathematica:
(x+y)sin(x-y)
And this is my in- and output:
Plot3D[(x + y) (Sin[x - y]), {x, -50, 50}, {y, -50, 50}]
The output is ...
- 27
2
votes
2
answers
86
views
Select and deselect many options at once in CheckboxBar
Is there any way to select and deselect many parameters in Manipulate's CheckboxBar? For instance, consider following code:
...
- 392
0
votes
1
answer
76
views
Speed up compoundReturn across an array
I am trying to calculate a moving-window of compounded returns on a large 2D-array. (ie some kind of MovingMap on geometric returns)
The Rows are time-steps and the Columns are different financial ...
6
votes
4
answers
322
views
Delete special part from a list using Mathematica
I have a list like this:
{{-0.0019,1},{-0.0018,2},...,{0,11},{0.001,6},...}
I need to make a new list that start from zero value. like this:
...
- 115
4
votes
3
answers
402
views
A loop in which three indices are changed
How could this piece of code be written in the Table, or as simply as possible?
...
- 1,731
1
vote
2
answers
84
views
1
vote
2
answers
147
views
Associating a string variable with a numeric variable
There is a translation operation from a numeric variable to a string variable:
a[i_, j_] := Symbol["a" <> ToString[i] <> ToString[j]]
How ...
- 1,731
1
vote
1
answer
163
views
Generating a table of squares and square roots up to 100
I want to generate a table of roots and perfect squares similar to the image, but I can't find the right code, I have searched the forum for something that works for me without favorable results. Can ...
- 2,247
0
votes
2
answers
120
views
2
votes
2
answers
88
views
Map, applying list in a defined function
Suppose I have defined some function (This is arbitrary)
F[alpha_,a_,b_,c_]:=List[alpha,a+b+c]
I want to apply this F for a given huge list of sets
...
- 801
1
vote
1
answer
75
views
Assigning each string variable to the corresponding element from the list inside a loop
I would like to assign values from a list l to variables g1, g2, ...
- 1,731
3
votes
4
answers
213
views
How to declare all list items are function variables?
There is a list xy = List[x, y] and an expression f = x^2 + y^2. I would like to get a function ...
- 1,731
2
votes
1
answer
129
views
Renaming a large number of elements
I have a lot of elements of this kind: a[1], a[2], a[3], ... I would like to rename each of ...
- 1,731