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1
vote
1answer
27 views

Scaling and Stretching a Mesh

I have a Voronoi mesh, given by ...
1
vote
1answer
22 views

How to sum like this

I want to sum as follows, where j is from 1 to n in each sum (if s is added to 2 when j is not added to n, then j does not need to be n): $$Table[\sum_{s=k,j=1}^{n}(s+j),\lbrace{k,0,n\rbrace}]$$ We ...
1
vote
4answers
70 views

How to draw $z =\rho^2+θ^2$ surface figure in cylindrical coordinate system

The following code is from here: ...
1
vote
0answers
14 views

Color of the evaluating cell brackets

What is the option to use in a stylesheet that controls the color of the brackets for cells in the evaluation queue?
0
votes
0answers
27 views

Frame ticks in scientific form on double $ y $-axis plot

I need plots with ticks on the $ y $-axis (both on the right and left) in scientific form as well as equally spaced (unlike in ListLogPlot) to plot data present in ...
0
votes
0answers
22 views

How to show the value of $ x $-axis based on $ y $-axis and saved into table?

I have a code here to calculate the value of y-axis of each partition based on mx. What I would like to do next is: To show the value of each x-axis from the ...
2
votes
1answer
36 views

Around formatting won't work with a imaginary number and small error

The new function of Mathematica 12, Around, is a replacement of the obsolete ErrorBar function from ...
2
votes
1answer
32 views

Find transfer function from system of equations

I have a system of equations, For example: eqns = {a1 x + b1 y + c1 z == d1, a2 x + b2 y + c2 z == d2, a3 x + b3 y + c3 z == d3}; and for this I need to find <...
7
votes
0answers
146 views

Can Wolfram Language enforce pure functions?

Is there a feature in Wolfram Language that supports or enforces pure functions? WL has something that it calls "pure functions" in its documentation, but these are most emphatically not pure ...
2
votes
1answer
29 views

Generating plot from a list of containing rules

Using Solve, I have produced the following list of solutions to an equation: ...
1
vote
2answers
51 views

How do I plot a definite integral on Mathematica?

I am not sure how to put this in good format, but I want to plot this on Mathematica: $$ u(t) = \frac{1}{4\pi t} \int\mathrm dy\ \mathrm e^{-y^2/(4t)}\ y\ (1 - y^2) $$ on the interval $ [a, b] $ ...
0
votes
0answers
21 views

How to get an image skeleton sharp with long lines

How can I get a straight skeleton of an image. 1@ just use vertical, horizontal lines in situation of image1. 2@ include tilted lines in situation of image2. Background, using least lines to ...
8
votes
1answer
66 views
+50

How to calculate border length between adjacent Voronoi regions?

I have a set of Voronoi cells that I partition into some defined regions. I would like to then calculate the length of the "borders" between these adjacent regions, using the edges of the underlying ...
2
votes
1answer
32 views

Defining a tensor from an expression of other tensors in xAct

There's been a number of people asking how to set a tensor-valued variable in xAct; equivalently, how to define a new tensor from an expression of existing tensors. For example, a very simple ...
6
votes
2answers
94 views

Operators without built-in meaning are incompatible with parallel evaluation

Mathematica has a useful set of Operators Without Built-In Meanings. For example: CenterDot, CircleDot, ...
2
votes
2answers
121 views

How to speed up this code with Bessel functions

I need to perform a ContourPlot on a function with BesselJ included. But my code is very slow, especially when I set the PlotPoints to be 100. I would like to know how to speed up this code. Any ...
4
votes
6answers
206 views

Generating list with short code

I need to get this list {1,0,2,1,3,2,4,3,5,4,6,5,7,6,8,7,9,8} with a very small code (< 30 characters) using Table and List functions. On each step, either it - subtracts 1 or - adds 2 I ...
11
votes
0answers
249 views

Undocumented TableView function

Seeking information on undocumented function TableView. Exempli gratia, tab=Table[Table[If[Mod[i,Prime[j]]==1,1,0],{i,1,10}],{j,1,2}] tab//TableView $ $ ...
1
vote
0answers
15 views

Are the conditions in ConditionalExpression necessary or sufficient?

I computed a limit and obtained it in the form of a ConditionalExpression (see below). Substituting the variables with numerical values in the resulting formula ...
1
vote
1answer
58 views

Cryptic NDSolve::nlnum when working with matrices

This problem was initially formulated in quaternions, but I had to rewrite them to complex matrices (as they seem to be supported better). Possibly introducing some errors along the way. So the ...
1
vote
0answers
13 views

TimeSeriesRescale seems to work oddly

I have been attempting to do some date computations with EventSeries, a convenient form for storing economic quantities (like expenses) over time. Following the documentation, I created an list of ...
0
votes
1answer
41 views

Lists forming figures

I would like to make a list whose elements form a disc when formatted. For example, this list forms a triangle when formatted ...
3
votes
0answers
34 views

Reduce quality of an imported MeshRegion

Importing STL files using Import results in a MeshRegion composed by the triangulation of the original file, and a similar ...
2
votes
3answers
32 views

cleaning up a list of values with no missing data

Im attempting to clean up a list which has missing elements by inserting the mean feature variable into the missing data ...
2
votes
1answer
54 views

How to convert linear equation to slope-intercept form?

Is there a general way (that can be applied to other linear equations too) to convert linear equation to slope-intercept form? For example, I have linear equation: $ 6x+3y=5 $ I want a method that ...
2
votes
0answers
23 views

Share package functions without sharing context

I'm trying to find a solution to a problem that I've been struggling with for a while. I asked a variant of the question here: Automatically load init.m without sharing CellContext, but think I've ...
1
vote
0answers
41 views

What does a single vertical bar mean in ConditionalExpression?

I got the condition below as part of a ConditionalExpression. Those single vertical bars before and after $\frac{1}{k1}$ appear to be an absolute value but I don't ...
4
votes
2answers
75 views

How to fill up the interior of the circles with red, blue and green colors?

ContourPlot[{x^2+y^2==1, x^2+y^2==4, x^2+y^2==9},{x,-4,4},{y,-4,4}, ContourStyle->{Red,Blue,Green}]
1
vote
0answers
38 views

AtomQ[Counts[{a, c, d, b, a, c, b}]] gives True. Why?

I don’t understand this: In[]: AtomQ[Counts[{a, c, d, b, a, c, b}]] Out[]: True It looks like an expression. Does this have to do with the realization ...
0
votes
0answers
30 views

Wigner 3j-symbol in mathematica

I am looking for a nice and workable formulation of the 3j-symbol in terms of hypergeometric functions. On the wolfram webpage I found: http://functions.wolfram.com/HypergeometricFunctions/...
3
votes
2answers
145 views

Solve equation in number theory

Let a belongs to the set Q\ S= { -1, 0, 1}. How do solve the equation below over S? x*a^(1/x) + a^x/x == 2a
8
votes
2answers
99 views

Independent RoundingRadius specifications for all corners

I need help creating a Rectangle (or Framed) where the roundness of each corner is specified separately. For example, I would ...
2
votes
2answers
61 views

How to simplify this sums of exponentials?

I got expressions that look like $$ \frac{1}{2} \mathrm e^{-\mathrm i r x} \left[\mathrm e^{2\mathrm i r x} \left(1 + \mathrm e^{-2\mathrm i x}\right)^r + \left(1 + \mathrm e^{2\mathrm i x}\right)^r\...
2
votes
1answer
65 views

Help: Obtain a huge amount of data solved in FrobeniusSolve? (perhaps better without running FrobeniusSolve?)

How to obtain a huge amount of data solved in FrobeniusSolve more systematically? I am interested in obtaining these two sets of data from FrobeniusSolve: ...
0
votes
1answer
18 views

building a graph from table of string records and array of keywords

I have a table of records, each record is about a publication onm some topic, the different colums indicating the title, authors, abstract and so on I made a function searchkeyword[string_] that ...
4
votes
2answers
46 views

String Cases Pattern Questions

Say I have the function: dep = TextStructure["He wrote a book. I read the book he wrote.", "DependencyStrings", PerformanceGoal -> "Speed"] Which outputs: ...
1
vote
1answer
39 views

how to scramble and then unscramble a list of elements?

list = {"a", "b", "c", "d"}; scrambledList=scramble[list] {"b", "d", "a", "c"} unscramble[scrambledList] {"a", "b", "c"...
1
vote
1answer
61 views

Homogeneous linear ODEs with time-dependent coefficient matrix, optimalisation of NDSolve algorithm

I would like to ask for advice on the following (probably not too complicated) problem: I have a linear system of ODEs of the following form: $$ \dot{X}(t) = M(t)X(t) $$ where $ X(t) $ is a vector, ...
2
votes
1answer
15 views

Converting string date to date object and retriving time difference

I am manipulating a text file, I need to extract dates from it, that will be in the format XJan__28_,__2020X where _ is either 1 or zero whitespaces __ is 1 or more than 1 whitespaces X is a ...
1
vote
1answer
1k views

Constraining FindFit to a range

I'm trying to fit data, that I obtained from measurements, to a theoretical model. The way I see it, FindFit or NonlinearModelfit...
1
vote
0answers
39 views

Simulating a partial differential equation, uniform vegetation and bare soil system (2 species)

I want to simulate a system of two plants ,woody and herbaceous species; with starting condition that half of the grid (square grid) is filled with woody specie, the herbaceous specie exist on the ...
0
votes
0answers
19 views

How to get the transformation function from one plane to another?

Suppose I have a plane which passes through some point $(x_0,y_0,z_0)$ and has a (normalized) surface normal $n$. Consider as an example a plane that passes through the point ...
2
votes
1answer
108 views

archimedian spiral from curvature

I am trying to reconstruct an archimedean spiral from its curvature $$\kappa (\text{s$\_$})\text{:=}\frac{s^2+2}{\left(s^2+1\right)^{3/2}};$$ eqns: $$\left( \begin{array}{c} t'(s)=\frac{\left(s^2+...
6
votes
3answers
467 views

Finding surface normal for 3D region at a specific point

I would like to find the surface normal for a point on a 3D filled shape in Mathematica. I know how to calculate the normal of a parametric surface using the cross product but this method will not ...
6
votes
3answers
371 views

How to make Minimize with Sqrt calculate faster?

This code ran a long time without getting a result (v12.0 & v11.3) Minimize[{Sqrt[3 + x] + Sqrt[3 - x*y], x^2 + y^2 == 9}, {x, y}] But with $x=3\cos t,y=3\...
4
votes
4answers
113 views

Extract strings containing digit characters with StringCases

I have a large string like this: string = {"text, 1998, TEXTDATA, text, 2007, NEXTTEXTDATA"}; Now I want to extract TEXTDATA and NEXTTEXTDATA. I tried to use <...
3
votes
0answers
179 views

an efficient way to evaluate this expression

Is there an efficient way to evaluate something like this? ...
2
votes
1answer
37 views

Plot in NDSolveValue

...
0
votes
1answer
32 views

Jacobian and Eigenvalues: is neither a list of replacement rules nor a valid dispatch table, \ and so cannot be used for replacing

I have seen many solutions to this error for finding jacobian and eigenvalues and tried but they are not working for me. Here is the code: ...
1
vote
0answers
30 views

how to rotate the elements in a list?

Given a list of elements: list = {"a", "b", "c", "d"}; What is an idiomatic way to move the first element to the end? ...

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