Questions tagged [list-manipulation]
Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
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ParametricPlot - Several curves by different parameters
I am trying to plot a set of curves f(a,b,t) along t with a,b = -10, -9, ..., 9, 10.
I can use Manipulate to draw 1 curve, and then change the curve shape by ...
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138
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Specifying the number of points sampled by NDSolve, and the meaning of "steps"
I am working with lists generated from interpolating functions given by NDSolve.
Manipulating the lists, I encountered a problem - the lists, of course, need to be ...
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How to plot data from table dynamically, without knowing how many columns are there?
I'm trying to read coordinates at certain times of Planets and Plot the orbit into a graph. For this example I'm doing this for eight planets, some coordinates from a table of some timesteps of the ...
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70
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Problem using ConstantArray in FindRoot
I ran into a strange problem, where using ConstantArray inside FindRoot results in a ...
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95
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Finding the main phases of the Moon in a particular month
My aim is to build a function that has parameters month and year and returns four lists, namely with the dates of the new moon, first quarter, full moon, last quarter.
This is more possible after ...
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TickMarks get different length inside function plotGrid
Mathematica 11.2 or earlier: I want to create a grid of plots and found this one by Jens excellent: https://mathematica.stackexchange.com/a/6882/245 :
...
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71
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Efficiently transform sequentially generated integer matrices into boolean matrices
Assume you have a list of 5 numbers, eg L = {14, 7, 11, 14, 0};.
Now, what you want to do with this list, is to transform each entry into eg a binary list, using <...
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Removing zeros from a list of equations
I am setting up a matrix system of differential equations that need to be solved. Some equations are redundant, and I have removed them using UpperTriangularize[]:
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Delete duplicates in a list compiled of different lists and also delete
I've got three lists: Lst1 has 100 different values for "r". Lst2 has 100 different values for "a". And Lst3=Pi*Lst1^2*Lst2. In Lst3 I've got duplicates and I want ...
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Proper syntax for DeleteCases with conditions
List is an array of dimensions {61777, 3}.
dist1 & dist2 are RegionDistanceFunctions.
Using:
...
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Using lists to access tensors like in MATLAB
I have a tensor of a variable size as an input to a function in which I need to access specific elements. Because the order of this tensor is variable, notation:
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Computationally Employ Sum over Ordered Partitions?
I have the following function defined, with two inputs $g$ and $h$:
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Format of numbers in a list
I wrote the below lines:
rang1 = Range[0.0, 0.4, 0.02]; rang2 = Range[0.5, 1.0, 0.1];
caten = Catenate[{rang1, rang2}];
I see
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- 1,503
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Exporting lists to text files with specific names
I am working with two matrices (because I have more matrices with indices (1,2,3,...) I write them below in specific format i. e. ...
- 1,503
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209
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Extract coefficients from CoefficientRules
So CoffeficientRules[] gives a vector {E1->c1,..., En->cn} for the N monimals Mi in the polynomial
P = M1+...+Mi
I would like to separate the coefficients ...
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Iterate over values in a table only if they are in a region
I made some pretty simple PDE's in non-square regions, and I am attempting to output the data (t, x, y, funcval) out to a .csv file (I know, terrible format for this, but it was a requirement for the ...
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Fill grid with list data
I have the following list:
list = {{114}, {59, 55}, {31, 28, 27}, {17, 14, 14, 13}}
The list data should be placed into a ...
- 2,356
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EmbedCode not evaluating a list of Manipulates
I have created a simple FormPage that asks for some user input, and should display a list of manipulates which are influenced by the given input. I use EmbedCode to display my results. The code I used ...
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indexing matrix computation by lists
I have a list of triangles stored as indices into a list of vertices:
...
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Problem with adding multiple tables from imported text file
Im having problems with performing operations on imported files and it is outlined as follows:
$1.$ Because of memory constraints on my computer, I used export that saves each iteration into a text ...
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409
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Accessing table extension in FITS file
I have a FITS file here that has no image but simply has a binary table in its extension. I have tried using Import["file","Tabledata"] but it returns an empty ...
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AirportData, GeoNearest and filtering data
I bought a Raspberry Pi, which introduced me to Mathematica, and I'm just diving in. I'm guessing my question is really a basic syntax question, but I don't know how to unravel it.
I thought I would ...
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Time-stepping an equation in Mathematica
I have an iterative integral equation of the form $$n(k,t+dt)=n(k,0)+dt\int_{0}^{\infty}dp\int_{0}^{\pi}d\alpha\int_{0}^{2\pi}d\beta\int_{0}^{\pi}da\,p^{2}q^{2}\sin(\alpha)\sin(a)\frac{(n(p,t)+1)}{\...
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Assigning Values of Indexed Variables to Arrays
New to mma. I have assigned the results of using Solve to solve 5 variables to 5 indices of a new variable:
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A problem of presentation of a matrix product inequality
I have 4 vectors or matrix
aa = {{a[1,1],a[1,2]},{a[2,1],a[2,2]}}
xx= {x[1],x[2]}
bb = {b[1],b[2]}
c = {<=, <=}
can I find an operation which gives
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Problem with the calculation of Lyapunov exponents
I am trying to calculate the Lyapunov exponents for the orbit of two bodies around each other. Therefore, I use the following code:
...
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173
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Plotting 3d lists with large data sets more efficiently
I have been trying to plot a set of 3D points using ListPlot3D. The list is very large, in fact Mathematica is even taking an excessive amount of time to calculate ...
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calculate new table from values of old table and find fit model curve
I'm new to mathematica and I'm struggling to figure this out.
I have a file with 6 space separated numerical data columns. Column 3 and 4 are the x and y values of the real data, column 5 and 6 are ...
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53
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Arrange of several files
I am struggling to import my data.
There are 400 files in CSV format with names organised by date like: Table1_20111003_YYYY_MM_DD_0000.dat. In each file over 20 colums and 86400 rows (seconds of ...
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List manipulation, averaging over lists and fidelity
I want to create vectors from a function poly[α_, β_, δ_, ϕ1_] were several variables (α, β, δ) are randomly sampled from a unit sphere. Then I want to vary another ...
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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 ...
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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:
...
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NIntegration and DSolve with same variable
I need to solve this problem:
Then follows the code, with:
...
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53
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Using Coefficient for Conjugate[variables] (Mathematica ignores my assumptions)
I have a sum and I use Coeffcient[] to extract certain terms. For example, I want all term in the following sum that contain ...
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56
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Concise use of list addressing
I very often work with Lists of Lists (trend data exported from other programs). Sometimes the start times of the important data ...
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91
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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. ...
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Defining an object which is function in some variables and tensor in some other indices
I am trying to define an object which function in some variable and tensor in other indices.
My attempt at it was:
...
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Lower memory usage and speed nested loops
I'm trying to make some tracking with Mathematica.
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Generate a list of values of a function for each value of the parameters already found
The following question is an extension of this question Find all roots of a function with parabolic cylinder functions in a range of the variable.
Now I want to use the roots found to calculate a ...
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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 ...
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Constructing a function for expanding general $n$ products
I have the following quantum mechanically motivated product:
$\langle0\vert(A_1b_1 + A_2b_2 + A_3b_3)(B_1b_1 + B_2b_2 + B_3b_3)(C_1b_1 + C_2b_2 + C_3b_3)$,
where $b_i$ is an annihilation operator ...
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Tracking solutions over a Brillouin zone
Thanks to @bbgodfrey I have a function that finds the two solutions to a set of equations bounded by a hexagonal region (corresponding to the Brillouin zone). It takes the angle ...
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158
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Autocorrelation of 3D Points
I'm trying to compute the autocorrelation of a list of points $(x,y,z)$ in 3D. Can the CorrelationFunction or maybe ListCorrelate...
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Make a table of changes in US coinage
I thought of an innovative use of Mathematica/Alpha that I think Stephen Wolfram would really love, but I can't figure out how to get it to work. The idea is to make a table that would chart the ...
- 4,048
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A more efficient way of fitting a non-linear model that returns an entire list?
I have a function that takes two parameters, del and nu, and returns a list npoints long ...
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Generating the set of all three-dimensional binary arrays distinct under rotation and reflection?
How can I automatically generate all possible three-dimensional binary arrays of size $(x_1 \times x_2 \times x_3$) where each array is distinct from all others with respect to rotation and reflection ...
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Making simultaneous equation solving more efficient
I am trying to solve a system of several simultaneous equations that have been generated by a series of modules and functions, using this module:
...
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