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

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16
votes
7answers
715 views

Enumerating tuples from a larger space such that all pairs of values are present at least once

I am trying to write a function that will accept a list of N lists and returns a list of N-tuples that represent all pairs of values from the original N lists at least once. To illustrate with an ...
3
votes
1answer
160 views

Easy way to perform multiplication of two 2x2 matrices, that contain list elements?

I have two 2x2 matrices, which elements are lists (so overall structure can be complicated). I need to perform matrix multiplication of these 2x2 matrices as if the elements didn't have its inner ...
6
votes
5answers
630 views

What is the best way to draw a shaded table?

I'm trying to format a raster-style table with row and column headings and in which each cell is shaded according to the value in the cell, and the value of the cell is displayed in as text in a ...
4
votes
7answers
185 views

Get the position of the right interval

I have a list of intervals: Intervals = {{0, 1}, {1, 2}, {2, 3}, {3, 4}, {4, 5}, {5, 6}} and a list of measurements: ...
15
votes
4answers
867 views

Exclude data from a list

Let's create some random sample data data = Table[{RandomReal[{-10, 10}], RandomReal[{-10, 10}]}, {i, 1, 300}]; Then we plot them using ...
12
votes
3answers
263 views

Using 0 to create new columns in a list with Part

I just discovered a nice way to create intermediary columns in a list, and I would like to know if I can have some problem with it. It Works like this: Imagine I have this list, 5x3: ...
6
votes
2answers
463 views

How to exclude some indices in defining Table?

Suppose I define a table using Table[n, {n, -n0, n0}] (where n0 is some positive integer) but I want n not to take the value <...
3
votes
3answers
400 views

Compare 2 lists

I want to compare 2 lists. One is very large and I need to compare many times. Lets say Length[list1] I need to know how many times list1 occures in list2. Eg. list1={1, 0}, list2={1, 0, 1, 0, 1, 1} ...
1
vote
1answer
126 views

Lists of integers coprime to another list

I have two lists of integers. The first, p, is a list of primes (for example, {2,3,5,7}). The second is a list ...
-1
votes
4answers
164 views

Eliminate symbols from Lists

I'm working with a list of roots of a 3rd order polynomial family, so i get a list this way: ...
0
votes
3answers
114 views

Manipulate list in function

I have some problems with lists and functions. Basically I just want to cut all entries from the right side, which contain 2. ({2,1,2} should become {2,1}) ...
6
votes
5answers
522 views

Efficient Indexed Sort

Suppose I have a preference for animals given by: orderOfAnimals = {"dogs", "cats", "fish", "elephants", "giraffe", "hamsters", "poodles"}; I'm given many data ...
0
votes
4answers
102 views

How to express “if any component in a vector satisfies that …” in Mathematica

For example, l is a list of vectors. I need to delete from l all the vectors with any component larger than 1. How should I do ...
0
votes
1answer
35 views

MapThread with incompatible length (How to Map twice in the same line)

l and b are two lists of vectors with different length. I need the list of vectors that is constructed by adding each member of <...
2
votes
4answers
551 views

Removing all values from a list that satisfy a given condition

Suppose I have a list, list = Table[{n}, {n, 1, 5}] (* list = {{1},{2},{3},{4},{5}} *) and I want to remove all values from this list that are greater than 3, so ...
1
vote
1answer
261 views

Error: in the part assignment is not a symbol [duplicate]

I am trying to set part of a Doubly-indexed list aInitialPopulation to cNumHeg. Specifically I am trying to set the 3rd part of the list aInitialPopulatiom[[cNodeNumber]] to cNumHeg. My (attempted) ...
4
votes
7answers
128 views

Distributing identifiers

I have a list that looks like this: {{"a",},{2010,0},{2011,10},{2012,27},{"b",},{2011,11},{2012,66},{"c",},{2010,19},{2011,20},{2012,}} I want to turn it into: <...
0
votes
1answer
89 views

Finding duplicates in a list [duplicate]

I have a list of integer, and I want to know if the list contains any duplicates. My code is working, but I feel there is a more straightforward way of doing this ...
2
votes
1answer
121 views

Excluding cases from Map

I'm doing operations of the form: PowerMod[#, -1, 126]+# & /@ Range[1, 125] When a number is not invertible, I don't want it to be included in the result set....
4
votes
2answers
133 views

How to sum values in the list that belongs to same week

I need to sum values that belongs to same week. For example, I have the list x with one column and n rows. Format: ...
3
votes
3answers
280 views

Finding the first position in a list that is over a certain value

Let's say I have the following list: L = {2,4,6,8,10} How can I get Mathematica to find the index position of the first value in the list that is over 4 (6 in ...
2
votes
3answers
84 views

How to manipulate one column of a table using the value in another column

Let's imagine I have the following table structure data = {{a, b}, {c, d}, {e, f}}; and I want to transform it into the following table ...
1
vote
3answers
215 views

A rule replacement problem: list -> list

Suppose I have a vector function f[x_] := {x[[1]]^2 - x[[2]]^2, Sin[x[[1]]] + Cos[x[[2]]]}; Then I want to make a list of gradients at some values: ...
1
vote
2answers
131 views

replace two elements in a list with the sum of those two elements?

I have a list: G[3] = {2, 4, 2, 4, 2, 4, 2, 4, 2, 4} (there's a 3 in there for the 3rd Prime) Recursively defined by: ...
1
vote
1answer
110 views

Modifying a list of matrices with conditional statement

I have a list of around 100 matrices, that looks like this ...
7
votes
4answers
458 views

Computing a map between two lists

What I want is a little difficult to explain. So I try to it with an example. I have 2 lists, each of which has $(n-1)^2$ elements. Each element is an integers between 0 and $n-1$, inclusive. For ...
1
vote
1answer
153 views

Histogram from a list of matrices

I have a list of around 100 matrices, that looks like this ...
1
vote
1answer
94 views

How to form a variable from matrix elements

I have matrix with n rows and 2 columns, say m = {{x11, y12}, {x21, y22}, ..., {xn1, yn2}. Now, I want to form three new variables for example: ...
2
votes
2answers
322 views

How to delete certain unwanted elements from an array

Suppose I have an array like so array1 = {{Null,2,3,4,5}, {a,b,c,Null,e}, {w,x,Null,y,z}} Is there some way to selectively remove any element I ...
1
vote
1answer
59 views

Multiway Systems Rules List Management

I'm working with a multiway system and I have a number of different mutation rule lists. I need an efficient way of managing which rule lists I apply. Here is the basic multiway system code that I'm ...
1
vote
2answers
156 views

Symbolic combinations

If I have 3 lists: {a,a},{b,b},{c,c}, then the desired output is ...
1
vote
2answers
73 views

Exporting mixed data of matrices and vectors / lists

thank you for reading my question. I have a problem trying to export mixed data from Mathematica. I have different matrices and vectors, which should be combined to a output file. Here a minimal-...
3
votes
1answer
205 views

Making a list of rules from the list of elements

Starting from the list: {f[q1, q2], f[q3, q4], g[q1], g[q2, q3, q4], d[k1 - q1], d[k2 - q2 - q3 -q4]} I would like to get the result: ...
3
votes
3answers
205 views

Pare down list recursively

What is the best way to pare down a list whereby the $n$th number is removed from the list recursively? This ...
1
vote
0answers
120 views

How to create a complex variable from dated list values

Can anyone help me to construct a variable "PI" from values of variable x. Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
5
votes
4answers
475 views

How to extract a part of matrix satisfying certain condition(s)

I have a following matrix ...
13
votes
6answers
3k views

Selecting every n-th element from a list

I have a list: data = {4, 5, 7, 8, 9, 5, 3, 2, 1, 2, 13, 12}; I want to take those elements in the list which are located at equal distances, say, every third ...
3
votes
2answers
110 views

MapThread problem

I would like to do the following: ...
4
votes
3answers
376 views

Extracting columns from multidimensional list

Perhaps a very easy question but I posted this on the Wolfram Community and didn't get any answer.. Suppose I have data like: ...
3
votes
1answer
157 views

Programming for matrix manipulation

I want to write a programme which operates on nd x nd matrices. The programme looks the matrix as a n x n block matrix where ...
4
votes
2answers
150 views

Can't figure out how to apply these functions repeatedly

I have the following problem, and even though I've tried Fold & Inner, Sow & Reap, et al. I can't figure out the clean way to do this. Here's the problem. I have a list that starts as ...
3
votes
2answers
67 views

Fast functional method for multiplying duplication numbers in a large list

Consider a list of symbols: mySet = {a, b, b, c, a, b, c, d}; I would like to form the product of duplication numbers. In the example above, I have 2 ...
2
votes
3answers
118 views

Manipulating array

I have got an array like this: A = {{{1, 4, 5}, {3, 7, 15}}, {{5, 6, 9}, {7, 8, 2}}, {{9, 10, 1}, {11, 12, 3}}} I make differences in each sublist a following ...
1
vote
2answers
134 views

How to select states with equal times

Can anyone show me how to select the states that have equal times-dates. For example, i have two time series. First that have 10 observations, say from 2014/10/1 to 2014/10/10, and second that have 7 ...
1
vote
2answers
246 views

Replace list of symbols in an expression

I have an expression: exp = a+b+c and a list containing all the symbols of my expression: syms = {a,b,c} and I would like ...
1
vote
4answers
136 views

Conditional combining of nested lists

I have two nested lists like those {{a,A},{b,B},{c,C}...{z,Z}} {{a,1},{c,2}...{t,12}}. I want to combine them to get a new list that looks like this ...
7
votes
2answers
293 views

Why doesn't this pattern work?

I want the in-built function Count to count the elements in a list which are greater than a value. Example: ...
-1
votes
1answer
154 views

Rotate points by 60° in 2D

I wrote this code, to rotate a list of points 60° about the first point in the list in 2D, but Mathemtica says: "Recursion depth of 1024 exceeded."
8
votes
6answers
2k views

Check if two lists are equal in any order

Suppose I have two lists, how can I efficiently check if the two lists are identical up to permutations of the elements? For example I would like the function to output: ...