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

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3
votes
1answer
138 views

How can I get a single solution to a set of inequality constraints?

I have a set of constraints to which I require integer solutions. However, instead of needing all possible integer solutions (as obtained by using ...
5
votes
1answer
285 views

Problem with creating a large list of tuples

This is a follow-up question from Sum of Multinomial Coefficients I have thought about the meaning of the formula I mentioned and, with help, I implemented the following code: ...
6
votes
2answers
372 views

Merging two Lists

I have two tables. One is given by T1 = Table[{x, y, 0.}, {x, 0, V},{y, 0, V}] and from a calculation I have the second, a list of points {x, y, z} ...
6
votes
3answers
162 views

How to 'merge' a list like FromDigits, but with a mixture of numbers and symbols?

How do I go from {C,4,G,5,S,7} to C4G5S7
3
votes
4answers
301 views

Mapping over the last level of a list, or equivalent operations

I would like to style each element of my list using Style. But when I try ...
10
votes
7answers
466 views

How can I Flatten this List with Inner List of Lists?

Given the following List ...
7
votes
1answer
1k views

Get the coordinates from ContourPlot and RegionPlot

How do I get the coordinates from a contour plot I've done in Mathematica? For example, I have a two-variable function f[x, y], for which I can make a contour plot: ...
-1
votes
1answer
95 views

How to separate a vector into two vectors, one having the first half of my original vector and the other having the second half

I have a set of n vectors with an even length. Let us make an easy example with 3 vectors of length=4: ...
2
votes
1answer
687 views

How to solve equations self-consistently

I want to solve the following equation self-consistently. So, H.u = e.u {{1, d}, {d, 1}}.{u1, u2} = e.{u1, u2} I guess an initial value for ...
16
votes
1answer
3k views

How to remove redundant {} from a nested list of lists?

There are numerous examples here, whose end result is the removal of empty brackets {} and empty lists. I still can't find an example of simply removing redundant ...
1
vote
3answers
169 views

Separate an array in two arrays, the even and odd terms being separated in these two arrays

How can I separate the odd terms in one array and the even terms in another array,i.e., go from a={1,2,3,4} to aeven={2,4} ...
1
vote
2answers
164 views

Subtract more than one array using DeleteCases

I need to create an array subtracting two arrays from another array. I know how to subtract one: am = DeleteCases[amp, Alternatives @@ af] I can subtract an ...
0
votes
1answer
71 views

How to get a number, but not a list, of the dimension of your array?

I need to use the dimension of a certain array, to use it as a bounder in a loop afterwards. The problem is that I get a list, when write : ...
-2
votes
1answer
252 views

Non-regular grid data

I have issue with non-regulary spaced data. I have set of 3 numbers {x, y, z} in my list. ...
1
vote
3answers
817 views

Loop through a list and select elements

I am new to Mathematica and I have no idea how to make a basic for loop work. I want to loop through the elements of a list: Range[45, 200]. I want to select the ...
3
votes
5answers
366 views

How to combine some elements of a list?

In order to simplify my expression, I face a list manipulation problem. For example, given the input list ...
2
votes
3answers
430 views

Selecting subsets of a list containing a specific element

I'm trying to generate all the subsets of a set containing a specific element. For example, for the set {1, 2, 3, 4}, with the specific element I want inside each subset being 4, the required answer ...
4
votes
5answers
139 views

Convert a list with three arguments {x0,x1, step} into an equidistant table?

How can I convert a list such as: a = {1, 2, 0.1} into sequence so that I can pass them into a function, e.g. I want to be able to do something like this ...
7
votes
3answers
360 views

Multiply a list of matrices by a list of vectors

How does one multiply a list of matrices by a list of vectors, elementwise? For example, multiplying ...
3
votes
2answers
152 views

Sequence and boolean And

I'm trying to figure out if a calculation result it's a valid result. As it return a matrix, I need to test that every element it's a number, so I thought this could work... ...
9
votes
1answer
200 views

Creating a number based on given conditions

In the grade 7 math curriculum here in Alberta we teach divisibility. I'm trying to write a program to create questions based on the idea of a student being given say, 4 digits, and then choosing ...
7
votes
4answers
423 views

Find list position and mapping list

Sorry, my English is not very good. I have two lists: ...
1
vote
1answer
129 views

Creating an array eval [closed]

How can I create an one dimensional array (a vector) evaluating a function of two variables? I know how to do it with one variable: Array[f, n, {a, b}] generates a ...
9
votes
2answers
294 views

Speed up 4D matrix/array generation

I have to fill a 4D array, whose entries are $\mathrm{sinc}\left[j(a-b)^2+j(c-d)^2-\phi\right]$ for a fixed value of $\phi$ (normally -15) and a fixed value of $j$ (normally about 0.00005). The way ...
7
votes
3answers
155 views

Given a list of lists, build a list in which lists with equal first and last elements are grouped together

I have a list of lists, and I'd like to build a new list, in which lists are in the same list if they have the same first and last element. Here's an example. Suppose I have ...
0
votes
1answer
114 views

Where do those nulls come from? [closed]

I have seen discussions of unwanted nulls in the output in the context of building lists with conditions on the elements, but that is not involved here. I would like to know where the nulls come from ...
3
votes
1answer
153 views

How to make a simple tree yourself with defined distances for each generation?

I'm trying to make a function that generates a tree for spin spin analysis in spectroscopy. I though it would be pretty easy, but I'm totally stocked. The tree should look something like this: ...
4
votes
2answers
222 views

Partition a set into $k$ non-empty subsets

The Stirling number of the second kind is the number of ways to partition a set of $n$ objects into $k$ non-empty subsets. In Mathematica, this is implemented as ...
3
votes
3answers
515 views

Sum of Multinomial Coefficients

Basically, I want to write a function to compute the following sum $f(m,L):=\sum_{0\leq k_1,\cdots, k_n\leq m} \binom{m}{k_1,k_2,\cdots k_n}$ and $\mathrm{supp}(k)=L \subseteq \left \{ 1,...,n \right ...
8
votes
4answers
392 views

Best way to modify values in a list of rules?

Recently I had to solve a problem similar to this: Let's say I have a list of list of rules ...
2
votes
1answer
109 views

Strange behaviour of variables in Table

I'm trying to work with some vectors and have run into a strange problem. An obvious way to define a difference of two vectors would be dif[x_,y_] := x-y I ...
7
votes
2answers
343 views

Finding all points of period n in an iterated map

I'm trying to implement an algorithm of Jenkinson and Pollicott to calculate the Hausdorff dimension of a Julia set for the map $f_c : z\mapsto z^2 + c$. It's described on page 40 of their paper, ...
9
votes
4answers
696 views

Passing large list by reference

I have the following problem: I would like to control evaluation of a variable that points to a list. For example, frequently in the code I have functions of the form that are supposed to work on ...
0
votes
1answer
486 views

Find Roots in Do loop

Task: Finding roots in loop t = List[1, 2, 3, 4, 5] fx[x_] := a*x^2 - 5 List[Do[Print[FindRoot[fx[k] == 1, {a, 1}]], {k, 0, 5}]] Output: Currently the output is ...
3
votes
2answers
216 views

Listable compiled function using Map

I'm trying to minimize the computation time of problem which is too long to post. I use compilein order to gain some speed. To increase speed I would like to use ...
0
votes
3answers
254 views

Finding an index with certain conditions

EDIT: I need to find out an index i which depends on certain conditions and I'm not able to implement it. I have a list (time points) $t_i$ and two constants $a,c$ ...
9
votes
5answers
506 views

Counting the population of integers

Suppose that myData is a list of sublists. Each sublist has a length of one or greater and contains any number of replicates of the integers 1, 2, 3, and 4. I ...
0
votes
0answers
60 views

get while loop output into a list [duplicate]

I would like to get the output from this while loop and use it as a list so I can count the frequency of the various tuples.. ...
0
votes
2answers
190 views

Converting a list of replacement rules into a list of real values [duplicate]

The following command outputs a list of replacement rules. ...
13
votes
3answers
374 views

Quick multiple selections from a list

What is the fastest way to make multiple selections from a list? Compiled methods included. For example, here are two methods for selecting a subset, compared:- ...
2
votes
2answers
344 views

Replacing values of a function

I have recently starting using Mathematica and have recently come to what seems as an impasse in my understanding of the language. If this is too "tell me how to do it" I would certainly understand. ...
9
votes
5answers
287 views

How can I remove matching sublists from my list?

I want to use DeleteCases (or any appropriate function) to remove elements of a list, which in turn are lists of fixed size. The rule I wish to apply is that any ...
6
votes
3answers
313 views

Delete elements from a list really fast

I have this bit of code that works, but it's very slow when there are 600k elements in the list: ...
0
votes
1answer
148 views

Discrete 3D plots of median ratios of two 2D matrices of lists of values

Lets say I have 2 2D arrays where each cell contains a list of values: Example: ...
4
votes
1answer
748 views

How do I find the Euclidean distance between one point and all the points in a list?

I want to find the Euclidean distance between one point (x1) and a list of points (y1), which contains a lot of coordinates x1 = killer[[2]] {6.05102, ...
6
votes
2answers
686 views

Elegant way to handle columns operations

Inspired by this question from @sjdh and by my recurrent use of columns operations in database sets, I was looking for one way to make columns operations more symetric, so I can handle with matrix and ...
1
vote
2answers
318 views

Generating a list of rules [closed]

This is my first time asking a question on this forum. I would like to generate a list with a range of numbers and use this list for a function to read from. Ok, now for the good part, it would look ...
3
votes
3answers
175 views

Count items in a list that occur before a date

I have a list of dates that happen throughout 2013. I wish to construct a graph showing a cumulative total of elements that happen before that date. I have a working algorithm, but it seems too slow ...
8
votes
3answers
516 views

How to rebuild original data from a histogram?

I have data in the following form. I have a list of values and a list of frequencies that indicate how often each value has occurred. Example list of values: ...