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12
votes
4answers
119 views

How to deal with loss of significance in the case $f(x) = \sqrt{x+2} -\sqrt{x}$?

I would like to evaluate the expression $f(x) = \sqrt{x+2} -\sqrt{x}$ with cases when $x = 3.2 \times 10^{30}$ and $x= 3.2 \times 10^{16}$. I tried using ...
2
votes
1answer
78 views

Quadratic form for specific formula as matrix reprezentation

So I have problem for specific formula to create Quadratic_form form from $$y = 3 + x_1 - 2 x_4 + 2 x_3 x_4 + x_2 (-x_3 + x_4) $$ as matrix \begin{bmatrix} 1 & 0 & 0 & 0 \\ ...
3
votes
3answers
54 views

Dots at points of discontinuity

So, I got this code: Plot[Piecewise[{{3, x <= 0}, {x^2 + 1, x > 0}}], {x, -2, 2}, PlotStyle -> {Purple}, Axes -> False, Frame -> True] and I ...
2
votes
0answers
41 views

Problem with antiderivative which involves DiracDelta

Let us execute in version 12.0 Integrate[DiracDelta[x]*DiracDelta'[x], x] DiracDelta[x]^2/2 and this lasts at least since version 7. However, the ...
0
votes
0answers
27 views

HermitianMatrixQ Ignores Assuming, $Assumptions

HermitianMatrixQ seems to ignore a variety of ways I tried to help it get the right answer. For example, ...
0
votes
0answers
35 views

Z-Transform Solution

I am trying to solve the z-transform of the following sequence using Mathematica: x[n]=-a^n u[-n-1] The known result is $X(z)=z/(z-a)$ with ROC: $|z|<|a|$. ...
0
votes
0answers
42 views
0
votes
2answers
105 views

Non-linear differential equation with tricky variable dependence

My problem regards solving a differential equation and can be reduced to the problem of finding $f(x)$ such that $\frac{df}{dx}=\frac{dh}{df}$, with $h(f)$ a known function. I have this list of data,...
2
votes
2answers
43 views
0
votes
0answers
22 views

Using URLExecute[] for online data acquisition

On the United Parcel Service website(UPS) there is a form where you can enter a zip code and it will return a color coded map that shows shipping times from that zip code. I am trying to use ...
2
votes
2answers
55 views

Select Part of a boundary mesh

I would like to pick a part of a boundary mesh, for example bm=BoundaryMesh[Cuboid[]] Is it possible to select the part(side) ...
4
votes
3answers
237 views

How can I get a “RedLevel” instead of GrayLevel when drawing a densityplot?

I was trying different colorfunctions, but don't get the RedLevel like the picture as follow: My picture is like this, a greylevel one.
3
votes
4answers
110 views

how to make tree plot to 100 rows

[ I know how to make finite tree plot(small row numbers), but how can I make this thing continue to 100 rows? Thank you very much!!
0
votes
0answers
35 views

Solving Integration with exponentials

I am trying to solve this integration : Integrate[(1 - Exp[-a*x])* (1 - Exp[-b*x])*(1 - Exp[-c*x]), {x, 0, t}] I get the result. But when I use the below ...
0
votes
1answer
107 views

How to solve the problem

I want to solve these equations for "r" and \theta. But, mathematica is unable to produce output. Can anyone help me please to find the values for "r" and \theta? Here, "k" can be fixed by 0.75. <...
1
vote
0answers
46 views

How to connect to LinkedIn

I want to draw a graph of a network of LinkedIn users/followers/companies, etc., using LinkedIn data. I tried this: SocialMediaData["LinkedIn", "Connections"] ...
0
votes
0answers
13 views

Apply Conditions on the Derivative of a Model with More Equations than Data in FindFit

Looking to combine the two approaches from these two posts here: How to Add a Constraint on the Derivative of the Model in FindFit How to fit 3 data sets to a model of 4 differential equations? ...
0
votes
0answers
26 views

How to fully simplify the reduce

Consider the following Reduce statement ...
2
votes
2answers
73 views

To find the point of Intersection of two line in Mathematica

How to find the intersection point of two lines exactly, the lines are generated using some data. The x-axis is on the logarithmic scale and the y-axis is on a linear scale. ...
2
votes
0answers
57 views

Error Message for GrammarRules and GrammarApply

I have been struggling with the following issue regarding an irregularity when deploying and applying GrammarRules. Specifically, it often takes several failed attempts before the execution is ...
0
votes
1answer
22 views

StreamPlot Failure

In versions 11.3 and 12.0, the following causes StreamPlot to fail: ...
0
votes
1answer
27 views

How to have NonlinearModelFit not evaluate a function too early?

This is a follow up of my previous question How can I define the following function for arbitray values of the arguments? that received no attention so here I will try to be more concise with the ...
0
votes
0answers
14 views

How to solve this problem by reading the data from table [closed]

When the driver drove 23km, what is the charge for the trip?
2
votes
1answer
50 views

What to use to draw errorbarplots in Mathematica 12.0 [on hold]

I have been using Needs["ErrorBarPlots`"] for a while but after my update to the last version of Mathematica I get the warning: ErrorBarPlots` is now obsolete. ...
0
votes
1answer
39 views

Why sum of two simple matrix is not in correct way? [closed]

clear[a]; a = List[{0, 1, 2}, {1, 2, 3}, {2, 3, 4}] a // MatrixForm; M2 = Transpose[a] // MatrixForm; a + M2 I am trying to run this code for ...
0
votes
1answer
44 views

Classifying numeric vector data [on hold]

Neural Networks seem so complex these days. Can anyone please suggest a simple structure (i.e. code) for training numeric vector data: examples of 24 numeric inputs to produce 1 (integer) numeric ...
0
votes
1answer
30 views

Expression with Boole

Let us have an expression for example, this: 2 (-1 + p) (3 - 4 p + 2 p^2) Boole[\[FormalX] == 1] - 9 (1 - 2 p + p^2) Boole[\[FormalX] == 2] ... For the whole ...
43
votes
2answers
5k views

Is there any algorithm that runs faster in Mathematica than in C or Fortran?

I'm just curious. My friend just told me that Mathematica is mostly for symbolic calculation and not efficient for Numerical computations. He told me that's the reason most of the people don't use ...
2
votes
0answers
21 views

How to extend External Language Input?

Is it possible to add a new option here and bind an evaluator? It seems that you can specify behavior by changing CellEvaluationFunction, but I don't know how to ...
0
votes
1answer
36 views

How to force Mathematica to give answer in certain functional form?

I want Mathematica to evaluate $$0=\psi (x) \left(\frac{k x^2}{2}-\text{En}\right)-\frac{\hbar ^2 \psi ''(x)}{2 m}$$ and give me answer in terms of the Hermite polynomials but it gives me result in ...
4
votes
1answer
105 views

How to track a deformable rod in video?

I have a video of nanotubes in solution taken with a confocal laser microscope. I typically track these nanotubes with Fiesta or Fiji, but in this case, there is variation in brightness that is ...
0
votes
1answer
38 views

How do I find horizontal asymptotes of f(x)=7x+2/sqrt 9x^2+4 [closed]

How do I find horizontal asymptotes of f(x)=7x+2/sqrt 9x^2+4
3
votes
2answers
287 views

How can I better manage memory usage when defining functions?

Suppose I have defined a numerical function F[x] that for each entry x, it takes a long time to calculate. Suppose that now I ...
0
votes
1answer
17 views

Maximize and minimize R6 function using Lagrange Multipliers

I've been trying to maximize and minimize the following function using Lagrange Multipliers, in Wolfram Mathematica 11.3: d = Sqrt[x^2 + y^2 + z^2 + u^2 + v^2 + w^2] Subject to the following ...
0
votes
0answers
26 views

I get different results with replacing the values with Replace all and manually replacing [closed]

R[n_, l_, r_] := Sqrt[(n - l - 1)!]/Sqrt[(n + l)!] 2^(l + 1)/n^2 (r/n)^l Exp[-r/n]*LaguerreL[(n - l - 1), (2 l + 1), (2 r/n)] ...
0
votes
0answers
43 views

I need a starter kit for Differential Geometry

In Modern Cosmology, the Geodesic Equation is described as:$$\frac {d^2x'^2}{dt}+\left[ \left( \{\frac{\partial x}{\partial x'}\}^{-1} \right)^l_i \frac{\partial^2 x^i}{\partial x'^j \partial x'^k} \...
12
votes
3answers
317 views
+100

Where is the numerical solving breaking down?

I am working with a set of three coupled reaction-diffusion PDEs, and for some parameter values I am getting some not so great solutions. I have been searching documentation and tutorials, and I have ...
2
votes
1answer
40 views

Does NonlinearStateSpaceModel work with symbolic constants?

I'm trying to put a nonlinear system of two 2nd order ODEs given by: ...
1
vote
1answer
56 views

Strange evaluation of Bessel Functions near $x=730$?

I am doing a calculation which involves the numerical evaluation of the following function: $$f(x)=I_0(x)K_0(x)-I_1(x)K_1(x)$$ where $I_{\nu}(x)$ and $K_{\nu}(x)$ are the modified Bessel functions. ...
6
votes
0answers
48 views

Status of DualLinearProgramming

DualLinearProgramming is referenced in this tutorial tutorial/ConstrainedOptimizationLinearProgramming It exists in ...
6
votes
1answer
34 views

Setup sharing of a directory on Wolfram Cloud?

I have a number of public notebooks with addresses like https://www.wolframcloud.com/obj/yaroslavvb/newton/lyapunov.nb https://www.wolframcloud.com/obj/yaroslavvb/newton/util.nb etc Is there a way ...
2
votes
2answers
42 views

Number formating in manipulate

This is closely related to this question.. Suppose I have a slider control for Manipulate. Can I display the slider label in percent (or, in general, any other ...
3
votes
1answer
67 views

BarChart and ColorFunction

There are really two questions. The first is: how does one get BarChart to generate x coordinates. That is, ListPlot takes a list of pairs, but ...
5
votes
2answers
113 views

Merge numbers to a new number and find digit on position \(n\)

I'm trying to construct a 'Mathematica solution' for the following 'puzzle' The natural numbers are placed in a row; 12345678910111213... What digit is the 10,000th digit? I don't know ...
0
votes
0answers
20 views

Log contour plot axis disappear after export to pdf [on hold]

I have the following code that produces a plot: ...
1
vote
0answers
91 views

How do I solve the integral over four spherical harmonics?

I want to solve this integral ...
0
votes
0answers
16 views

SemanticImport adds garbage characters to key name

I want to import a csv to a dataset. This exact dataset successfully imported on a PC, but on a Mac one of the columns has garbage characters added to the key (see below example). I don't believe ...
0
votes
0answers
15 views

Summation involving complex conjugate pairs [on hold]

Consider the prime counting function $$\pi(n)=R(n)-\sum_{\rho} R(n^{\rho})$$ where $R$ is Riemann's function (link) and the $\rho$ are the non-trivial zeroes of the zeta function, taken in ...
2
votes
1answer
19 views

How to specify coordinated of legend box using Show and Epilog functions?

I am trying to place the legend box using epilog function. I'm unsure where I can specify the coordinated in the sample code to specify the position. ...
0
votes
1answer
77 views

Why is lisa[i_, j_] :> Nothing un-evaluated?

Anyone know how to correct it with minor change? Input...

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