# Tagged Questions

Questions on the numerical functions of Mathematica, implementing numerical methods and numerical computing with Mathematica.

0answers
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### Is it possible to get the error estimates of predicted values computed by FindMinimum using the Levenberg Marquardt method?

I use the LevenbergMarquardt method of the FindMinimum function to minimize a residual function (mathematical-optimization). This residual function is computed from experimental data and the solution ...
1answer
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I am trying to numerically solve this Volterra type integral equation. The equation I'm plugging in is a simplified version of We will take $H(\eta')$ and $q(\eta)$ to be 1 for now. $\mu$ is = $\... 2answers 93 views ### How to find the integrand singularity points when having NIntegrate::slwcon: In order to calculate the closed area of the curve below defined by parametric equation curve02, ... 1answer 50 views ### My NIntegrate expression returns a wildly inaccurate value I am trying to integrate a function using NIntegrate: ... 1answer 97 views ### Results of ArgMax as a function of a parameter with InterpolatingFunctions I would like to obtain a function and its derivatives, where the function is defined as the solution to a maximization problem. The obvious approach ... 0answers 44 views ### EvaluationMonitor and variables with indices + subscripts I have encountered the following problem while using EvaluationMonitor with NMinimize: variables that have both a subscript and an index, e.g. Subscript[x,y][1] do ... 3answers 1k views ### Funny behaviour when plotting a polynomial of high degree and large coefficients I am trying to plot a polynomial of degree$29$on the domain$[0,1]$, with fairly large coefficients: ... 1answer 98 views ### Funny behavior when computing dot product of coefficients with high-order polynomials I have a similar problem to Funny behaviour when plotting a polynomial of high degree and large coefficients. However, the thing being evaluated is not just a polynomial but a dot product of some ... 1answer 137 views ### A weird issue with Interval[$MaxNumber]

From the Interval documentation: For approximate machine- or arbitrary-precision numbers x, Interval[x] yields an interval reflecting the uncertainty in x. <...
2answers
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### Numerical approximation using trapezoidal formula [closed]

I have bumped into a problem, that I cannot solve. I have to approximate the value of ln3 using a composite trapezoidal formula, so that the error should be within (10)^-3! How can it be solved?
5answers
6k views

### How can I differentiate numerically?

Mathematica has two ways to integrate: Integrate and NIntegrate. But what about D? ...
3answers
4k views

### Numerically solving Helmholtz equation in 2D for arbitrary shapes

I would like to solve the Helmholtz equation with dirichlet boundary conditions in 2 dimensions for an arbitrary shape. (for a qualitative comparison of the eigenstates to periodic orbits in the ...
4answers
272 views

### How to find the next root larger than a specified value, numerically?

I would want to have a general-purpose, reasonably robust method of finding the next numerical root above a specific value of x. I'm stumped by the fact ...
1answer
157 views

### Errors Solving Elliptic PDES with FEM

I am trying to solve the equation below governing transversely isotropic plane strain in cartesian coordinates with the given boundary conditions based on code found here using Mathematica 10.1 on OSX ...
0answers
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### strange FullSimplify result, why zero? [duplicate]

This came up looking at this How to speed up calculation of this equation (FindRoot). Is there some sense to why FullSimplify gives zero here? ...
1answer
733 views

### How to work with Experimental`NumericalFunction?

This question is intimately connected with previous one: "How to create internally optimized expression for computing with high WorkingPrecision?" Oleksandr R. correctly states in the comment: A ...
1answer
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### Solving a nonlinear systems of coupled differential equations with boundary conditions

I am trying to solve the following systems of coupled differential equations with boundary conditions (BC) at $0$ and at $∞$ : \$y_{1}'(x)=\frac{-\sqrt{\frac{2}{\pi}}\,\frac{\alpha}{18}\,x^4+x\,y_{2}(...
4answers
628 views

### How to remove duplicates from set of machine precision 2D points?

I have a set of 2D points with machine precision coordinates. I need to remove all duplicates. Performance is important. This is the most obvious fast solution: ...
1answer
237 views

### Breaking out of NDSolve

I am solving a coupled set of differential equations with NDSolve for 6 unknown functions of time. At a certain point in time, the system hits a singular point ...
2answers
549 views

### Symbolic derivatives are being calculated numerically

Just found the following while debugging a problem. Mathematica is calculating the derivative of IntegerPart[x] in some odd way: ...