Questions tagged [numerical-value]
Question relating numerical representations, operations and methods, including approximate results instead of exact symbolic results.
284
questions
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1answer
58 views
Numerical integration with poles
I have got many errors for this integral. Anyone knows how to fix it? (I am using mathematica12.2)
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2
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1answer
69 views
How to get numerical value of functional derivative at specific point
I have a functional in the form:
$$F[s(x)]=\int_0^1(s(x)-a(x))^2\mathrm{d}x$$ where $a(x)$ is a parameter function, and I would like to find the functional derivative of $F$ with respect to $s$.
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1
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1answer
49 views
Double numerical integral, in two steps
Let me define the following function:
f[x_] = x
I have to solve the numerical integral:
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1
vote
1answer
76 views
Smart way to do a numeric integral of a recursive function defined by symbolic integration
I have a little question. I need a smart way to compute a numerical integral.
The standard way to compute a numerical integral, in multiple variables, is, for example, the following:
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3
votes
2answers
163 views
Numerical values of Fox H function
I am playing around with the new function from 12.3, FoxH and found the result is not stable. It is interesting that the results are pretty different with the introduction of higher accuracy, and the ...
0
votes
1answer
121 views
Numerical integration of a function with Dirac delta
I have a little question about the numerical integration of a function that includes a Dirac delta.
I have the following function:
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3
votes
1answer
57 views
Which one is more accurate Solve or NSolve? How can I get the same result as Solve using NSolve in the given code?
I am using this code to calculate the quantity $sol$. Using Solve, I get the result $9.8598$
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0answers
29 views
1
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1answer
51 views
Getting strange result with derivative of Abs of a complex number
So I am getting some results after a computation like:
(-0.741446 - 5.47358 I) Abs'[-0.702207 + 0.0951203 I]
The problem is the derivative in ...
3
votes
2answers
61 views
Blank plot with numeric data
I seem to be getting a blank plot even though the data provided is clearly numeric and plots fine with other data. I just don't see what is special about this data that results in a blank plot.
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0answers
74 views
Why does Mathematica store numerical values in a fresh kernel?
For some reason, when I try to do a computation in a fresh kernel, MM remembers the "old" values from the old kernel, is there a way to stop this?
1
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0answers
124 views
How to numerically solve this system?
Our system:
\begin{align}
\dot S &= \mu -\beta_1 S I_2 -\beta_2 S J-\beta_3 S A - \nu S\\[2ex]
\dot {I_1} &= p \beta_1 S I_1 +q \beta_2 S J +r \beta_3 S A + \xi_1 J- b_1 I_1 \\[2ex]
\dot{...
0
votes
1answer
44 views
Is always possible to define a numerical value using subscript?
In this code I defined some values using subscripts and it is not the first time I did this but strangely the code execution crashes. To follow the code.
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3
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0answers
66 views
Avoiding underflow with equations of the form $\binom{n}{x} p^a (1-p)^b$
I have the need to evaluate equations of the form
$$\binom{n}{x} p^a (1-p)^b$$
where the values of $p$ are between 0 and 1 and $n$, $x$, $a$, and $b$ can be very large numbers.
I attempt to use
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0
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0answers
64 views
what's wrong with this code for truncation number m=9?
I have a puzzling problem over the following mathematica code I program to solve some problem. I believe the two plots as defined are identical, but it is only identical when mm<9 and when m is ...
1
vote
1answer
53 views
0
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3answers
46 views
NSolve not giving a solution
I have a parameter set
paramFinal2 = {\[Beta] -> 0.2, \[Alpha] -> 0.5 , c -> 0.150, b -> 0.1, \[Kappa] -> 1};
I define the following variable
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0
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0answers
70 views
Can't create matrix function of symbolic functions and assign values to elements
So I have a problem regarding the symbolic matrix value assignment.
Say I create a matrix function as:
P[t_]:= {{P1[t]}, {P2[t]}, {P3[t]}};
Then I want to assign ...
0
votes
0answers
47 views
Numerical minimization of function
So I have the following equation:
3 Sqrt[9.15753*10^-6 + 25.1556 TolC^2 + 25.1556 TolL^2]==1;
Now TolC and TolL can take respectively the values of these lists:
<...
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0answers
42 views
Evaluate an expression with numerical values
I hope this time you guys can help me. I have the following numerical expression:
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1
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2answers
104 views
Efficent ways to use NSolve, Reduce
hope you're having a nice day!
Context: I'm trying to constrain parameters from a model of Orbital Resonance equilibrium. In short, I know a parameter "$\Delta_{eq}$" which is derived from ...
2
votes
3answers
204 views
1
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1answer
90 views
Is there any alternative for NSolve or Solve to obtain all the roots of the given function?
I have this function for reals $0<x<\pi$.
$$f(x)=(3 \pi -2 x)^2 \sin \left(\frac{1}{2} \left(\csc ^{-1}\left(\frac{4 \pi (\pi -x) \csc \left(\frac{\pi ^2}{\pi -x}\right)}{4 x^2-8 \pi x+5 \pi ^...
0
votes
0answers
40 views
How can I make sure if the given function has any roots which are not rational multiples of $\pi$?
I have this function for $0<x<\pi$.
$$f(x)=(3 \pi -2 x)^2 \sin \left(\frac{1}{2} \left(\csc ^{-1}\left(\frac{4 \pi (\pi -x) \csc \left(\frac{\pi ^2}{\pi -x}\right)}{4 x^2-8 \pi x+5 \pi ^2}\...
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0answers
56 views
NMaximize computes wrong value
This question is a continuation of NIntegrate with a complicated function over the 4-sphere . Now I define a certain new function called "improvement" via:
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0answers
87 views
1
vote
1answer
39 views
Phenomena between ill-conditioned and well-condtioned
Given that I have the following sparse matrix:
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1
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1answer
59 views
how we can extract the value of the solution of a PDE in a point x? (NDSolve) [closed]
Please I need your help, I calculate the solution of heat equation using methode of line
This is my code:
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0
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1answer
34 views
0
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2answers
53 views
How to improve the calculation accuracy and speed of double numerical integration？
I want to solve the following double numerical integral:
$A=\int _{0.52}^1\int _0^{\infty }\frac{\sqrt{s^2-0.52^2} \sqrt{1-s^2} \left(2 s^2-1\right) \left(\left(2 s^2-1\right) \text{T1}-2 s^2 \text{T2}...
0
votes
2answers
89 views
Nested NIntegrate over a region: Numerical Integration not converging
I need to computed two double nested numerical integrals, of which one is defined over a specific region (e.g. a pentagon). I've tried to use a single NIntegrate with four variables, but the result is ...
1
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1answer
63 views
2
votes
1answer
158 views
Does this series converge or diverge?
Let us consider the series $\sum_{n=1}^\infty \frac {\{\sqrt n\}-\frac 1 2} n$, where $\{\cdot\}$ denotes the fractional part
of a real number. On the one hand,
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0
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0answers
89 views
(Urgent) NSolve not working and visualization of solutions
I want to solve a system of three equations and 3 variables numerically with NSolve, but it either takes an eternity and doesn't give me a result or it gives me an error message that the methods ...
2
votes
0answers
68 views
NSum complaining of being non-numerical
I am trying to evaluate the sum $\sum_{k,l=1}^{30}\frac{1}{(k^2+l^2+1)^{5/4}}$ so I write
NSum[1/(1 + k^2 + l^2)^(5/4), {k, 1, 30}, {l, 1, 30}]
but I get a message ...
0
votes
1answer
68 views
Non trivial zeros of Dirichlet L function
So I was wondering if I can find some of the non trivial zeros of the Dirichlet-L function using mathematica. What I found out was there is a code ZetaZero[] which ...
4
votes
0answers
95 views
How to use NDEigenvalue to accurately estimate functional determinants?
Goal: Ultimately, I would like to find a trustworthy approximation for the ratio of the functional determinant of two differential operators using the formula
$$ \frac{\text{Det}[\hat{D}_0]}{\text{Det}...
5
votes
1answer
203 views
Problem with NDSolveValue
I am trying to solve some 3D PDEs (for example, 3D diffusion equation) with step function or DiracDelta function as initial condition. I know those functions have discontinuity so I use some ...
0
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0answers
27 views
1
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0answers
74 views
Is there already a program that analyzes THz-TDS data in Mathematica?
I plan to write a code that reads the time domain data(sample+reference), performs Fourier transforms, calculates transmissivity, solves the transfer function numerically, and gets complex refractive ...
1
vote
1answer
94 views
Solving a system of transcendental equations
I am trying to solve the following system of transcendental equations:
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1
vote
1answer
77 views
How to obtain numerical solutions of a system of two equations with two unknowns?
I have two equations with two unknowns $-10<x<0$ and $0<y<15$
$$3 y \cosh (4 x) \cos (y)+(2 x+5) \cosh (x) \sin (y)=0,\\3 x \cosh (x) \cos (y)-(2 x+5) \sinh (x) \cos (y)=0$$
I would like ...
20
votes
1answer
723 views
Is Internal`StringToDouble broken in 12.3?
I believe Internal`StringToDouble was the only way to fast convert string into numbers. Now in V12.3 it was removed:
Internal`StringToDouble["1"]
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0
votes
1answer
44 views
Numerical value of Derivative of Dirichlet L function at some particular points [closed]
I want to find the numerical value for the derivative of Dirichlet L function to compare with an another formula. However I am not able to obtain any numerical values. I tried to use
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1
vote
1answer
117 views
Solve using PolyGamma function
I am trying to solve for the value of y.
My code is:
x = 0.165;
f = -Log[y] - PolyGamma[0.5 + 0.2*(x/y)] + PolyGamma[0.5];
Solve[f == 0, y]
Running gave me
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0
votes
1answer
109 views
How do I install the " FourierSeries` " package?
Can anyone tell me where are the packages for Wolfram Mathematica 11.2 ? How do I load them?
0
votes
1answer
60 views
Is it possible to ask Mathematica to give all the roots of the given function?
I have this equation
$$ 36 \cos \frac{3 x}{4} \cos \frac{27 x}{20} \left(\cos \frac{3 x}{5} +2 \cos \frac{21 x}{10} \right)=0 $$
Is it possible to ask Mathematica to give all the roots of the ...
0
votes
2answers
65 views
a generic way to deal with intermittent non-numerical values in arrays
Sometimes when dealing with arrays with intermittent non-numerical values (e.g., NaNs imported from external sources), the common arithmetic functions (e.g., ...
0
votes
0answers
32 views
Mathematica CSV values
I wanted just to add constant to each value. i. e.
data = Import["/Users/paul/Desktop/rtm1.csv", "CSV"]
And I get
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0
votes
1answer
59 views
NSolve missing solutions
I'm having trouble solving the transcendental equation. For some values of bi, NSolve obtains 6 roots, however when changing the value, it obtains 5. Graphing the function clearly shows that the ...
