Questions tagged [numerical-value]

Question relating numerical representations, operations and methods, including approximate results instead of exact symbolic results.

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15
votes
3answers
2k views

Solve Laplace equation in Cylindrical - Polar Coordinates

Hey mathematica stackexchange!! I've got a (possibly stupid) problem. I've tried many things to no avail, and I've read every post I've found on Laplace's equation. Background: I'm trying to find the ...
8
votes
2answers
3k views

Could I define 0^0 to be 1? [duplicate]

Many occasions, where I need to work numerically with functions. For a variable strictly between 0 and 1, during the optimization, it could become 0.^0 or 0^0, which then become indeterminate. Is ...
3
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1answer
182 views
3
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2answers
266 views

How can one generate an open-ended sequence of low-discrepancy points in 3D?

I'd like a low-discrepancy sequence of points over a 3D-hypercube $[-1,1]^3$, but don't want to have to commit to a fixed number $n$ of points beforehand, that is just see how the numerical ...
3
votes
1answer
551 views

Recognize physical constants?

Is there some way to ask Mathematica to recognize physical constants, such as 32 or 9.81 (gravitational acceleration, in different units, at Earth's surface)? I have in mind something like the "...
7
votes
3answers
246 views

Different Methods in NIntegrate

I am trying to numerically calculate a multidimensional integral which involves Jacobi elliptic theta functions. The integrand is the following: ...
3
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2answers
605 views

How to obtain numerical solutions of a two-variable equation?

I have a two-variable function: f[x_, y_] := (4 y^2 - 6) (Cos[y π] Cos[x] - Cos[2 y π] Sin[x]) How can I find all the numerical solutions for $x$ and $y$ such ...
2
votes
3answers
442 views

Re-arranging / selecting of a data table very slow in For loop [duplicate]

My task is quite simple; I have a table of data like M = {{1,2}, {1,3}, {3,4}, {5,1}, {6,9}, {6,8}, {6,1}}; so the table is sorted with respect to the first ...
1
vote
3answers
1k views

Why is 1. x (Times[1.`, x]) not simplified to x?

This is maybe a silly question, but I could not think of any logical reason why it is not simplified automatically. I was working with a big linear equation system with some constrained inequalities ...
19
votes
2answers
833 views

Error and uncertainty propagation: Is using Precision/Accuracy a sound strategy?

Questions What are the available resources to deal with experimental error and uncertainty propagation in Mathematica? Given that Mathematica already uses linearized model of error propagation on ...
34
votes
2answers
741 views

GroupBy twice gives different results

Bug introduced in 7.0 or earlier and persisting through 11.1 It took me quite a lot of time to finally trace down to this strange output. I really don't know why. First, I create a list ...
3
votes
2answers
472 views

Solving an equation approximately

I have a complicated equation in terms of $\omega$ and $\kappa$: ...
4
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1answer
726 views

Fixed-Point Numbers in Mathematica

I am working with a library that needs input in a Fixed Point notation. I’d like to figure out a way to convert the floating point results into fixed point representation. The fixed point length is ...
3
votes
1answer
104 views

Laplace equation DirichletCondition ignored

My goal is to find out force between two parallel identical disks with Voltage difference. To solve this, I tried to use laplace equation. And below is my code. where R is radius of disks, d is ...
2
votes
1answer
2k views

How to use NIntegrate in a function using parameters from a list

I would like to use NIntegrate in a function with some parameters from a list. I simplified my problem for this forum. The list of parameters is as follows: ...
8
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2answers
368 views

Why does N[Re@f] give complex result?

Consider this code: ...
5
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1answer
141 views

1-D PDE with nonlinear ODE as boundary condition

Recently, I am trying to solve a 1-D PDE with a nonlinear boundary condition using the function NDSolveValue. However, it seems that MMA (12) cannot solve it directly with some computational issues. ...
5
votes
3answers
242 views

How to plot output data of Do-command?

The following in a simple numerical solution of the simple harmonic oscillator. ...
3
votes
1answer
128 views

Solve a system of 4-th order polynomial equations (numerically)

I have a function defined on $ S^6 \times S^6 $ (two spheres embedded in $ \mathbb{R}^7 $ individually). Let us call this vector $ \vec{f}(\vec{x},\vec{y}) $, where $ \vec{x} $ and $ \vec{y} $ are ...
3
votes
2answers
135 views

Role of Accuracy in numerical evaluations, SplitBy vs GatherBy

This is a follow-up question to this question. I generated a list by substituting the results of a solve[] routine and set: ...
2
votes
2answers
773 views

Center column heading in TableForm

I have a TableForm as follows: ...
1
vote
1answer
38 views

Setting the parameters in a defined function vs replacement rule in the formula

I have the following definition in my Mathematica notebook. ...
1
vote
0answers
82 views

Why the data from Do-command disagree with the plot I get using them? [closed]

This is a question relevant to How to plot output data of Do-command? The Differential Equation at hand now is $\frac{d^2 f}{dx^2} + \frac{2}{x+0.1} \frac{df}{dx} = k(f)$ I give the code with the ...
0
votes
2answers
144 views

Product of large number with a very small number returns zero because Mathematica sets the very small number equal to zero [closed]

I have a product Exp[-I*Pi*x]*BesselK[-1, 2.43*Ix]. Now, Exp[-I*Pi*x] grows larger and larger as $x$ increases for imaginary ...
0
votes
0answers
92 views

Maintaining working precision in my program

I am badly stuck with this program I am writing. I want output of program below to be precise up to 25 digits after decimal point. I am supplying all inputs with precision 25. But after each iteration ...