# Tagged Questions

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

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### Why is Mathematica destroying this graph?

Here I have a picture of a function I graphed: reg[x_,y_]:=(x^2+y^2)Cos[4ArcTan[y/x]]; Plot3D[reg[x,y],{x,-2,2},{y,-2,2},AxesLabel->Automatic] And here is ...
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### Why can Mathematica compute numerical sums more efficiently when they are written as matrix operations?

Let $f(n)$ and $K(n,m)$ be functions such that the double sum, which we wish to evaluate numerically, $$\sum_{n=1}^a \sum_{m=1}^a f(n) f(m) K(n,m)$$ exists when $a$ is some large positive number. I ...
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### How to calculate accurate answer in Mathematica?

I accidentally discovered for myself, that Mathematica outputs inaccurate answer. For instance, if I take $\sin(2 \cdot \pi \cdot 0.5) = 0$, then in Mathematica it is: But if I calculate it on ...
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### Precision in calculation [duplicate]

I am writing some code to demonstrate the effect of the number of significant figures a coefficient has on the solution of a nonlinear equation. I define the coefficient as follows: ...
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### Difficulty in replacing variables with list of variables for a function for FindMaximum application

FindMaximum gives incorrect answer when I redefine a function by changing its arguments from variables to a list of variables. The code goes as follows ...
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### How can I solve a Hamiltonian with numerical methods?

Hamiltonian in terms of two level atom's operator (0 is ground state and 1 is excited state) which are 2*2 matrices and cavity modes are given by $a$ and $a^\dagger$. Rest of the parameters are ...
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### Transform a variable's exponent from an exact rational to an inexact decimal

here is a little problem I could not find a solution for. I have a variable with an exponent represented as a fraction, for example, var = a^(39/106) Now I ...
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### 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, ...
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### My NIntegrate expression returns a wildly inaccurate value

I am trying to integrate a function using NIntegrate: ...
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### Evaluate numerically an extremely small number

How to evaluate numerically $e^{-4 \cdotp 10^{35}}$ in the form $0,a_1a_2...\times 10^{-n}$ ...
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### What is the fastest way to compute digits of $\pi$ using Mathematica?

There are a lot of ways to calculate digits of $\pi$ using Mathematica. The most naïve way I can think of is N[π, 100000000] Of course, there are a lot of fast ...
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### solving with numerical methods [closed]

Hi I would like to solve the equation below in Mathematica.Since I am a beginner I can not solve it with NSolve and Solve.I don't know why.Do you have any idea?! ...
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### 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 ...
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### Plotting Planck's function and unexpected results

I have the code below. If you look at the plot, you can see a strange behaviour. The function goes to zero as λ->0 but you can see the plateau below ...
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### Can't sort my list numerically for larger numbers than 10 e.g. 1,10,100,2 [duplicate]

I want my files names in real numerical order so 1,2,3,10,12. However it is currently putting them in order like so: 1,10,12,2,3 Input: ...
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### Low accuracy while solving a multi-variable equation numerically

My question is as following: I was trying to make a function Vs2[r] with two parameters fit a set of conditions. Vs2[r]: <...