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.

learn more… | top users | synonyms

0
votes
0answers
34 views

A function that takes in an array and returns an array (or lists)

So I have function f[x_] := c.x - Total[Log[b - A.x]] where the variables have dimension c is 1x100, b is 500x1, A is 500x100, and x is 100x1. My goal is to get the ...
0
votes
1answer
39 views

Reduce array to specific amount of averages

The main issue which needs to be solved is: Let's say I have an array with 8 numbers, e.g. [2,4,8,3,5,4,9,2] and I use them as values for my x axis in an coordinate system to draw a line. But I can ...
0
votes
3answers
69 views

How can I create a four dimensional plot (3D space + color) of the data provided? [duplicate]

I would like the x, y, and z axes to be reserved for the first three columns and the color to be reserved for the fourth column. I would like the output to have a color bar and color function. If you ...
1
vote
2answers
43 views

TexForm List with Rule

I'm having some difficulty TexForming a list. The output is not what I want. The following is a minimum working example. I've tried every combination of Flatten, ArrayReshape, and Partition to no ...
1
vote
0answers
35 views

Find best convex approximation of an “almost convex” function

I've got values of a function of two variables at integer points inside a rectangle, that is, a rectangular table $f(i,j)$, $1\leqslant i\leqslant m$, $1\leqslant j\leqslant n$. The function is very ...
0
votes
1answer
30 views

Iterating KroneckerProduct[] and returning the result from a function

I am trying to write a function which will take a matrix m and an integer i as inputs. Then it will compute the Kronecker product of m with itself i times and return the result. The code is as ...
0
votes
4answers
50 views

insert elements into 2 D array [duplicate]

say I have a 2 dimensionsal array like a={{1,2,3},{4,5,6},{7,8,9}} and a vector like v={10,11,12} I want the result to be ...
1
vote
1answer
51 views

Rearrange the list with some rules

I am trying to solve physic problem on operators which are not commute. However, I am not good at coding, so I am having some problem with Mathematica code. Let's define my list such that ...
0
votes
1answer
54 views

Append[] is not working for empty list [duplicate]

I am trying to create an empty list and add an element but the list is not being populated. My code ...
-1
votes
1answer
91 views

Lattice model array for distribution of energy [closed]

Edited for clarity I am trying to make a 2-D array constant, lets say 100x100, and perform a function on that. The array would look like ...
0
votes
1answer
55 views

Calculation of the mean of array data points lying under a predefined rectangle

I have data points in an array, and a predefined rectangle lying within the area of my array. My goal is to calculate the Mean ...
0
votes
1answer
83 views

How to ListContourPlot a functional eigenvalue spectrum?

We have a (Hermitian) matrix of some finite dimension (n) whose elements are functions of real variables x and y. We wish to plot contours of the spectrum (level sets of the n real eigenvalues) at ...
0
votes
0answers
30 views

Simplify expression?

Suppose I have expressions that involve terms like: p1.p1+p2.p2+p3.p3+p4.p4 p1, p2, p3, and p4 are all elements of an array: ...
3
votes
2answers
56 views

Numbering indices / array element positions while creating an array (using 3 argument form)

I am new to Mathematica and trying to create a list that I can use within the InterpolatingPolynomial function. e.g. ...
0
votes
0answers
52 views

Splitting an Array

Background: I'm a fairly experienced programmer, but new to Mathematica I have an image analysis function I have created, which returns a multidimensional array that I do some processing on. I want ...
1
vote
1answer
71 views

making Max and Min work columnwise like Median

I have some data and the rows are grouped according to astGroupsPos (the astGroupsPos are just rows from ...
1
vote
1answer
45 views

Array Flattening arrays of matrices given by rules

Fix an $n$ and an $m$ positive integers.I have some set of four $n\times n$ matrices $A$,$B$,$Y$,$Z$ (where $Z$ is the zero matrix). I'd like to input the $nm\times nm$ matrix of block matrices given ...
2
votes
2answers
77 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
62 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
306 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
175 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
72 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
549 views

Finding center of mass in a 2D array

I have a 57x57 array with some integer values in it: ...
1
vote
2answers
80 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
95 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
65 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
116 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
91 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
50 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
97 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
55 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
26 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
78 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
176 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
39 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
73 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
94 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
177 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
216 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
54 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
98 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
445 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
59 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
64 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
130 views

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

Let's consider the following: ...
2
votes
4answers
208 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
81 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
83 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
74 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
826 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. ...