Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
7,094
questions
0
votes
0answers
38 views
calculate differences of a list using slots
I want to calculate the differences between the numbers of a list. One way to do that is using 'Differences'.
For example:
L = {1, 3, 6, 9};
Differences[L]
this ...
4
votes
2answers
129 views
Integrate function returns vector instead of scalar
When I try to integrate a function mapping a vector to a scalar Mathematica "ignores" the function and returns a vector independent of the function.
Here is a minimal example of my problem: ...
3
votes
1answer
61 views
Return the factors of a partially-factored polynomial, without factoring
Suppose I have an integer polynomial f that is in a factored form, say f = (1 + x) * (2 + x + x^3) * (2 + x^5). I want a ...
4
votes
1answer
121 views
How to filter table from some rows without flattening it?
Consider the following table:
a1[x_] = If[x < 1.1, 3, Pi/2]
tabb = ParallelTable[{x, y, z, a1[x]}, {x, 1, 2, 0.1}, {y,
0.5, 1, 0.1}, {z, 1, 3, 1}]
Here, a1[...
0
votes
2answers
46 views
How can I transform the string to a list?
As you can see from the picture, when I use StringReplace function, the list is converted to a string. How can I get the list form back? And the String "-" is necessary (Cuz I just know one ...
1
vote
1answer
31 views
Reading off coefficients as array
Suppose I have a series expansion with non-associative characters, i.e.,
$1**2**3**4**5 + 2**3**4**5**1 + \cdots$
Then I want to make some array which produces
$A[1]= \{1,2,3,4, 5\}, A[2]=\{2,3,4,5,1\...
1
vote
1answer
28 views
Call part of a replaced list
I have what I believe to be a very simple problem. I want to use an equation which depends on the values inside a list, but to be able to evaluate that equation with different lists. So:
...
16
votes
1answer
260 views
Head[x] vs x[[0]]
Can we say Head[x] and x[[0]] are identical ?
In mathematica manual I could find : 'The head is the part with index 0'
But I am not sure whether Head[x] are x[[0]] are really interchangeable in any ...
0
votes
1answer
53 views
Checking variable A is determined. (DeterminedQ ?)
How can we (loosely) check whether variable A is determined, not directly computing A ?
(= How can we define DeterminedQ function ?)
For example,
...
5
votes
2answers
117 views
Delete complex conjugate in a list
I have a list with complex numbers. I would like to delete a number $z$ that is in my list if at least one of these conditions is met:
$-z$ is also in the list
$\bar{z}$ is in the list
$-\bar{z}$ is ...
4
votes
3answers
94 views
Cases in list with varying length in sublists
Given
t1 = {{14, {{1, 2, 3}}}, {15, {}}, {16, {{0, 0, 4}}}, {17, {{0, 1, 4}, {2, 2, 3}}}, {18, {{0, 3, 3}, {1, 1, 4}}}, {u, {{1, 0, 2}, {2, 3, 0}, {2, 3, 4}}}}
I ...
1
vote
1answer
67 views
3
votes
1answer
64 views
Distribute a nested list
I would need a function that distributes a nested list in a specified position.
A sample of this function could be:
...
3
votes
2answers
77 views
Generating representatives of rotation classes of tuples of ones and zeros with a fixed number of ones
In a related question I asked how to generate all the tuples of ones and zeroes with a fixed number of ones (generating tuples of ones and zeroes with a fixed number of ones). I wish to consider a ...
7
votes
2answers
200 views
How Can I Compute The Automorphism Group of a Matroid?
I want to compute the automorphism group of a matroid. This reduces to the following (more general) problem:
Suppose I have a list of sets $\{\{b_{11},\dots,b_{1k}\},\dots,\{b_{k1},\dots,b_{kk}\}\}$ ...
2
votes
1answer
51 views
How to use IntegerQ on list?
t1 ={0, 1, 2, Log[6]/Log[2], 3, Log[12]/Log[2], 4, Log[24]/Log[2]}
I want to get the Position of the Integers. I can do it by
<...
5
votes
4answers
293 views
How to map a function with boolean operators over an array?
I am a beginner in Mathematica. I have this in Mathematica v12:
A = {1, 1, 1, 1}
B = {2, 2, 2, 2}
A+B
(* 3,3,3,3 *)
I'd like to experiment with evaluating ...
5
votes
3answers
367 views
Fastest way : two by two list inversion
Consider a list of even length, for example list={1,2,3,4,5,6,7,8}
what is the fastest way to accomplish both these operations ?
Operation 1: two by two element ...
6
votes
4answers
122 views
Check if list is singleton in sub linear time
A singleton is a list whose elements are equal. Some ways of checking this in Mathematica:
{Equal@@#&,
1==Length@Union@#&,
MatchQ[#,{x_ ..}]&}
I ...
9
votes
6answers
384 views
generating tuples of ones and zeroes with a fixed number of ones
I would like to generate all the tuples of ones and zeros of a given length and with a given number of ones without generating all the possible tuples, which is impossible for tuples of large enough ...
1
vote
1answer
34 views
How to convert element's Table to List / Array to make an independent multivariable fit?
I would like to make an independent multivariable fit, but I have problems using a Table that I generated. I can´t use their elements because it isn´t in a list or a rectangular array.
Using Table[ ] ...
0
votes
0answers
23 views
How to set PDE coefficient as a list of discrete data
How to set a pde time-dependent coefficient, not as an analytic function in time, but as a discrete data vector or list, each element of that list represents the coefficient value on a specific time ...
0
votes
1answer
47 views
Speeding up Do loop with lists inside
The question is simple. I'm trying to improve the (time) performance of a "Do" loop that looks like the following MWE
...
1
vote
1answer
129 views
How to efficiently replace the repetitive sequence?
The problem is how to determine the repetitive sequences and replace the part with consecutive sequences
For example:
A={{1,3,4},{2,3,5},{1,6}}
Then, detect there ...
2
votes
1answer
69 views
Another basic question on list manipulation [closed]
Suppose you have a list of triples:
A = {{x1,y1,z1},{x2,y2,z2},{x3,y3,z3}}
How do we find x such that z is the maximum?
2
votes
3answers
205 views
Basic manipulations with lists
Suppose I have a list of the following form:
List={{{a,b,c},{d,e,f},{g,h,i}},{{j,k,l},{m,n,o},{p,q,r}}}
I have two questions:
A) How can I convert this to a list ...
0
votes
1answer
68 views
Why won't Sequence work when wrapping a list of arguments for deletion with Remove?
I wrote a quick and dirty little function freshStart which does a variety of things meant to give me a nearly fresh Kernel without having to ...
3
votes
1answer
49 views
warning in Position + IntersectingQ
Why there is a warning message (with correct output) for the following code ?
...
0
votes
1answer
47 views
Sorting terms in a huge equation by grouping specific products
I have a boundary condition for a problem, which contains around 100 terms! I have no trouble getting Mathematica to compute it, but the terms are sorted in a seemingly random order and I would like ...
1
vote
0answers
30 views
How to select only non-numeric data from the mixed table [closed]
Consider the following data:
data={{1,2,3},{2,3,4},{1,5,Some symbols},{00,230,Some other symbols}}
where "Some symbols" is something arbitrary (say, a ...
3
votes
1answer
36 views
Using Apply or unpacking lists for only some arguments of a function [duplicate]
Say I have a function f of three parameters and a list l = {b,c}. I want to pass the first parameter to ...
10
votes
2answers
235 views
Efficient method to find a pair that sum to a given value in a list in matematica style
Given an array nums and an number target, find all pairs in array whose sum is equal to ...
0
votes
1answer
51 views
Comparing and finding element of a list [closed]
Let's say i have a list
tab1={{0.378377, 1.58249*10^-11}, {0.44749, 1.03208*10^-13}, {0.513543, 2.13122*10^16}, {0.505355, 7.12295*10^16}}
and i would like to find ...
0
votes
1answer
69 views
How should I export data with desired precision to output file
I want to control the number of decimal points in the output file.
...
1
vote
2answers
60 views
Binomial like multiplication of elements of a list
Given a list
p = {0.10715, 0.08058, 0.00360, 0.00183}
how to implement function that does:
...
1
vote
1answer
45 views
Find maximal elements of list (remove dominated elements)
Suppose I consider a to be greater than b if a[[1]] >= b[[1]] and ...
1
vote
0answers
60 views
List mean and standard deviation [closed]
I have a list indexk (in=Head[indexk] out=List)
its dimensions (in=Dimensions[indexk] ...
0
votes
1answer
58 views
How to efficiently find elements in list A that aren't in list B?
Every element in List A appears only once, and the same is true for List B.
How can I efficiently create a list of the element in A that don't appear in B?
Obviously, I can just do this:
...
2
votes
4answers
133 views
Plotting after solving equations
I obtained a list of Y list after using Table[NSolve[expression,X],{var,varmin,varmax,step}]. Then I created a list of X with ...
1
vote
1answer
69 views
How to use 'Join' and '& /@' : combining all .csv files in a directory into a single .csv file automatically
I would like to import all .csv files in a directory and combine them into a single file using Join. I can do this manually but when I try to automate it using <...
2
votes
3answers
167 views
How to join points {x1,y1} and {x2,y2} only if x2-x1==1
Given
list={{5, 3}, {9, 5}, {10, 4}, {11, 3}, {13, 3}, {14, 4}}
I want to ListPlot these points and use ...
2
votes
0answers
49 views
Handling lists indexed with integer partitions
I am trying to do some exploration around the multi-dimensional version of [truncated moment problem], where I work with various distributions (uni- or multi-variate), and use some truncated moment ...
2
votes
3answers
107 views
9
votes
1answer
182 views
Strictly Increasing Sequences of Length n in a List
I need to determine how many strictly increasing sequences of a certain length (e.g. 5) are contained in a list of integers. I would be very happy if someone could help me. A sequence would be ...
3
votes
3answers
171 views
Create list of rules from list [duplicate]
I want to create a dispatch list (list of rules to replace parameters) from a standard list.
I have an equation which depends on a, b, c, d. I want to pass lots of different values from a data set.
...
0
votes
1answer
54 views
Part Specification is longer than depth of object & Transposing Errors
In trying to recreate results from another question I had asked (here)
Code is:
...
3
votes
3answers
73 views
How to delete consecutive commas in an imported array in Mathematica?
I am importing an excel sheet into Mathematica. The result is a rectangular array. The array contains sequences of commas. Whenever a cell is empty in the Excel sheet consecutive commas appear in the ...
4
votes
2answers
69 views
From list to unique ID number AND back
If I have a series of list of the form $L_k=\{a_1, a_2,...a_n\}_k$ with $-4<a_i<4$ and $a_i\in\mathbb Z$, then I can make a unique ID number for $L_k$ using ...
1
vote
1answer
34 views
using a list of parameters in NSum [closed]
I am trying to make a function that uses NSum, that takes a list of parameters. But NSum doesn't appear to play nicely with lists. A minimum working example is:
...
11
votes
4answers
539 views
Scan through (partial) tuples
I have a list of list of positive integers $s = \{s_1, s_2, ..., s_k\}$, each list $s_i$ is possibly of different lengths, and I want to find out if there exists a $k$-tuple of the $s_i$ that sums ...
