Questions about Mathematica arrays, or implementing array data-type functionality, i.e, collections of regular dimensions containing elements that can be accessed by standard (computable) indices.

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2
votes
2answers
73 views

Multiplying a table with constants

I have a table with coordinates {{x1,y1},{x2,y2}} that I want to multiply with a separate constant for x and one for y so: ...
1
vote
0answers
57 views

Finding correct combination of functions

I am trying to write code where I have an array $S$ or numbers in any order [5,4,2,1,....] Then I have a specific set of functions that I can write. ...
15
votes
2answers
300 views

Which elements of a large array are part of a set?

I have a large integer packed array arr. My array is multidimensional, but for simplicity let's consider 1D arrays for now. ...
3
votes
3answers
165 views

Optimizing a series of basic matrix operations—scaling doesn't seem right with matrix size

I have a simple operation that I'd like to apply to an n×n matrix. My problem (well, one of them...) is that it runs in, say, 4 seconds for a 100×100 matrix, but it took five and a half minutes to run ...
1
vote
1answer
61 views

How to find the detailed Dimensions information of a list

In 5 digital images I have determined the 2d coordinates of detected objects. The resulting array (list) can be downloaded from here: http://pastebin.com/7bE0CEJ5 ...
3
votes
5answers
427 views

Finding center of mass in a 2D array

I have a 57x57 array with some integer values in it: ...
1
vote
2answers
72 views

Sum of a set of elements in a array?

For a function I do this (Integrate over circular range): NIntegrate[x*y Boole[Sqrt[x^2 + y^2] < 3], {x, 1, 5}, {y, 1, 5}] ...
1
vote
1answer
92 views

Using a table as a variable in a function

I have a bunch of arrays and need to extract specific rows and columns of these that obey certain criteria. So for one table I'd do like this ...
0
votes
1answer
54 views

Getting numerical values from integrated interpolating function [duplicate]

I have a list of data. I integrate them with interpolation. Lets say is the following: InterpolatingFunction[{{0.01, 4.82}}, <>][x] However, is that ...
1
vote
2answers
112 views

Trouble adding elements to array [closed]

I need to generate array and export it to file. For n = 1 , second element must be 0 For n = 2.. 819, second element must be 1 For n = 820.. 1637, second element must be -1 For n = 1638.. 16384, ...
5
votes
1answer
67 views

ListConvolve with Padding -> Fixed?

The built-in function ImageConvolve takes a Padding option that "specifies what padding to use when extending beyond the ...
2
votes
1answer
44 views

Create array of “positions”

How do I create an array a of generic depth $n+1$, such that exactly: a[[i1]][[i2]]...[in]] = {i1,i2,...,in} ? In words, such ...
1
vote
1answer
82 views

Using ReadList to import specific arrays of a multi-dimensional variable

Consider a large numerical variable (almost 1GB) which was constructed like below: output={scalar1,{Matrix1,Matrix2,Matrix3,scalar2}}; I used ...
2
votes
0answers
54 views

Arrays with two different types of indices

Is there a way of having arrays which have, so to speak, two different depths $m,n$? From the point of view of memory usage, it would be the same as an array of depth $m+n$, but I would like to ...
1
vote
1answer
23 views

Evaluate function entrywise on high dimensional array [closed]

I have defined a function $f$ from number to number. I want to tell Mathematica to apply that function to each entry of a high dimensional array $A$, to get a new array $f(A)$ in the same form of $A$. ...
2
votes
0answers
76 views

Dynamic array in Mathematica like malloc in C++

I have a table to describe a crossroad. Each traffic line has it own Q(flow), V( speed) and direction. I'm saving data in array, which hardcoded (very simple code data = {{66, 55, 3}, {44, 33, 2}, ...
4
votes
1answer
143 views

Drawing a RegionPlot but for data instead of a function

I am trying to draw something similar to RegionPlot, but instead of functions I only have data matrices. For example, I have the following 3 pieces of data ...
0
votes
0answers
37 views

Could not access a specific element of ConstantArray, why ? partw error [duplicate]

I could not access a specific element of ConstantArray, why ? The following is piece of my code: ...
0
votes
1answer
51 views

How to store value of result in an array for a calculation inside the loop [closed]

Note: In my code I used j (ranging from 3 to 7) but I want j to be general I tried this ...
1
vote
1answer
85 views

How hard is it to export numbers that can be used in other programs? [duplicate]

I am calculating a few lists of values that I have in arrays. I want to export these into a tab-delimited text file that I can import into other programs for analysis, plotting and so on but I am ...
3
votes
3answers
169 views

How to test if elements of an array are real or complex?

I am new to Mathematica and I have to select the elements in an array that only contain real numbers and eliminate the ones that have complex parts. Basically the code that I have is an array of ...
10
votes
1answer
145 views

Fast way to pass an array of integers to Java using JLink

I am using a package from java to compress a list of integers, this package provide me two methods, one for compress and other one for uncompress. Each of these methods has a version to ...
0
votes
1answer
46 views

How to create pairwise difference matrix entry?

I have a $16\times 1$ array of integer entries named $H$. How do I create a $16\times 16$ pairwise difference matrix between all entries in array?
3
votes
1answer
86 views

How to use Compile to generate an $n×n$ array using $n$ tensors with both Real and Integer element

This is an extension of my earlier questions Faster use of Condition for a large array (see the example) and How to use Compile to generate an $n\times n$ array using $n$ vectors . In this case each ...
1
vote
1answer
248 views

Export data from Array to *.csv without curly brackets

I have a couple of *.csv files containing data from several experiments. From those, two columns shall be extracted each, to form a new list. This process shall be automated to collect all the data ...
0
votes
0answers
55 views

Solving matrix optimization

I have the following problem. Let $X_1, X_2, \cdots, X_k$ are $n \times n$ Hermitian matrices (need not be positive) given. Let a $n \times n$ positive matrix $A$ is given such that $Tr(A.X_j)<0$ ...
0
votes
2answers
56 views

Defining an array of functions with multiple indices and one variable [closed]

I have a function f of one variable x and a 4 x 3 array ...
3
votes
1answer
126 views

How to use Compile to generate an $n\times n$ array using $n$ vectors

Let's consider the following: ...
2
votes
4answers
207 views

Is there a way to use array of data as a function variable?

I have a data that looks something like. {{1,1},{12,1},{7,9},{10,14}, ...... } I want to see if there is an easy way to apply this array of data into a ...
1
vote
1answer
57 views

Change data form Table to Array

Ok, I am trying to figure out how exactly to change the data from Table such as ...
3
votes
2answers
77 views

An conditional Sum of elements in Array [duplicate]

Consider we have: list = {{2, 3}, {3, 30}, {3, 2}, {4, 53}} and we want to compare the first elements and sum the second elements if first elements are similar ...
1
vote
1answer
71 views

How to specify positions in a matrix by an array?

If I have an array of sets of points such as pts = {{2,4},{1,3},{5,7}} Is there any super short command to use those pairs to output their respective elements in ...
13
votes
3answers
636 views

Subtracting two plots from each other after shifting one

I have the following lists representing energy spectra that need to be subtracted from each other to produce a difference spectrum. ...
0
votes
0answers
67 views

Handling really large Arrays (by possibly using lower precision) [duplicate]

I know there have been a few questions about efficient memory storage on mathematica.stackexchange, but I could not find a sufficient answer for my problem (except that it might not work at all). So ...
1
vote
0answers
60 views

Problems with indexes in a Do-cycle and CoefficientArrays

I have a system of linear equations with variables $A_n$ and need its coefficients in a matrix form (Transform linear system into a matrix form). I'm trying to do that through a ...
0
votes
1answer
719 views

Minimizing using indices, error: Part::pkspec1: The expression cannot be used as a part specification

I want to use Minimize where the variables to minimize are indices pointing into an array. Here a MWE that hopefully shows what my problem is. ...
0
votes
2answers
125 views

recurrence equation, result members don't contain the number 5 [closed]

print the first 5 members of the array a[n+1]=3*a[n]+7 which don't contain the number 5. a1=6. so a[2]=3*6+7=25, but 25 has the number 5 so we go to a[3]. a[3]=25*3+7=82 <--- this is OK... and ...
2
votes
1answer
110 views

How to construct a kernel from a function?

I would like to convolve an image with a mathematical function. I understand that I need to have the mathematical function in a matrix form. How can I build it? Thanks
1
vote
2answers
136 views

Slicing multidimensional table

Say I have a multidimensional list created in the following way grid= Table[{i, j+1, k+2}, {i, 0, 1}, {j, 0, 1}, {k, 0, 1}] grid={{{{0, 1, 2}, {0, 1, 3}}, {{0, 2, 2}, {0, 2, 3}}}, {{{1, ...
4
votes
0answers
77 views

Using indexed array elements as integration dummy variables with EvaluationMonitor. Bug?

As part of a routine that must cope with integration of varying numbers of dimensions, I would like to use indexed variable names (e.g., x[0], x[1],...) as dummy integration variables. However, it ...
1
vote
1answer
187 views

Plot a numerical integration as a function of a variable

Suppose we have a function that is hard to evaluate analytically but a numerical estimate suffices. For example consider the $f(x,\Lambda) = \Lambda\cdot \sin(x)$ where $\Lambda$ is some parameter I ...
0
votes
0answers
70 views

How can I find all stationary points? i.e Something like MinDetect but for saddle points (that applies to data arrays of arbitrary rank)

I would like to find all stationary points of a data set of arbitrary rank. MinDetect and MaxDetect are great for finding minima and maxima but I can't find a good way of finding the saddle points. ...
3
votes
1answer
167 views

How do I create an array by applying a function to the index of each element?

I am looking for something like matrix(m, n, f), but for Mathematica rather than MuPAD, and for arrays rather than matrices. That is, I'm looking for a(n ...
1
vote
3answers
249 views

Writing code to update a large matrix?

How can I write a code to update a matrix based on certain rules? I plan on constructing a large matrix, and I cannot submit entries one by one. The rules for the matrix are as followed: $$ ...
1
vote
1answer
83 views

Calculating a function repetitively without using a For loop

In my programme I have defined all these functions: ...
1
vote
3answers
82 views

Fill an array, symmetric with respect to its centre

I want to create an array that must be symmetric with respect to the centre of it, as in the following example: 0 1 2 3 4 3 2 1 but, instead of having such ...
3
votes
3answers
204 views

Creating a matrix under conditions

I would like to create a matrix whose elements satisfy the following conditions ( Mathematica 9 ) ...
0
votes
1answer
103 views

How to input an adjacency list?

I am a beginner user of Mathematica, and I have an assignment to construct a graph given n (number of vertices) and an adjacency list. My idea was to make a For cycle that repeats n times, and for ...
3
votes
2answers
208 views

Dynamic arrays and lists with compile (Append, Linked lists etc.)

I have a code that I need to compile. The code contains a loop in which I need to gather data into a list. The question is how to best gather data so that the code works inside Compile. The following ...
1
vote
1answer
65 views

How to extract a contiguous s_1 x s_2 x … x s_d subarray from an n_1 x n_2 x … x n_d array, where the dimension d is a variable

Given a multidimensional array, such as the 3-dimensional 2 x 2 x 3 array { {{a,b,c},{d,e,f}}, {{g,h,i},{j,k,l}} } How can I extract an arbitrary 3-dimensional ...