Questions tagged [numerical-value]
Question relating numerical representations, operations and methods, including approximate results instead of exact symbolic results.
368
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Solving a 3+1D Wave Equation
I am having some problems with finding the solution to the magnetic field, B[x,y,z,t]. Is there anything I can change to my code to obtain a solution of B[x,y,z,t] with the initial conditions and ...
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39
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How to find optimal solution
I want to ask something. Right now, I want to try to find the optimal solution from a function in a paper. here is the function :
And here is the numerical example :
There is solution procedure that ...
3
votes
2
answers
40
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Strange behavior of MinimalBy [duplicate]
data = {{1, 2}, {2, 2}, {3, 3}};
MinimalBy[data, Norm@# &]
Output: {{2, 2}}
When applying numerically :
...
2
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0
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55
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Interpreter fails to obey significant figure specifications
Consider the following example, where we specify the precision of the numbers to perform a significant figures calculation:
...
2
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1
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105
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Finding roots for an expression with non-elementary function
Is there an approach to solving this for $a$ in either closed-form or numerically?
...
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1
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65
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How to use multiple output from Nsolve? [closed]
I have 3 simultaneous equations and 3 unknowns. The values are coming to be right. But how do I assign these 3 values in the respective variables?
...
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2
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136
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How to numerically find complex non-real roots of a function?
Using Mathematica, how can we numerically find only complexes, but not real roots, of a function?
For example, if we have f:C->C, and we have roots like, R1,R2,...,Rn (real roots, without imaginary ...
1
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0
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60
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How to Parse Binary .STL File Created on Ancient 32-bit Architecture
Import[fileName,"STL"] returns $Failed
The file format is so simple that one can calculate the number of triangles in the file
by counting the number of BinaryReads to reach EndOfFile.
https:...
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1
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113
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Can't solve equation numerically (Solution in terms of Root) [duplicate]
I am trying to solve the following equation numerically.
...
2
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1
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125
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Solving a ODE (Peeble's Equation) with initial condition a the maximum input range
I have a differential equation which is,
$$
\frac{d X_e}{dz} = \frac{C_r(z)}{H(z)}\times \frac{1}{(1+z)}\Big[\frac{38\eta T^3}{25\pi^2}\alpha (T)X_e^2 - b(T)(1 - X_e) \Big]
$$
Where
$$
\alpha(T) = \...
1
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1
answer
64
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Is a four-variable function less than one?
I have the following function of four variables
f=Sqrt[(1 + w - x + 4 y z) - Sqrt[4 (-w + x) + (1 + w - x + 4 y z)^2]]/Sqrt[2]
I want to show that $f(w,x,y,z)<1$...
3
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58
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Derivative[0, 1, 1][QPolyGamma] cannot be calculated numerically?
During a more complicated calculation, I got an expression
...
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2
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105
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Why can't NSolve find values that FindInstance can?
I am trying to solve for \[Epsilon], given three input paramters n, x and ...
5
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1
answer
175
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Why is Around omitted when the uncertainty is zero?
I have a list of values with errors and I use Around[x, dx]. Some of those values have an error of zero though. Mathematica removes the ...
0
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0
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67
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NSolve can't solve a system of 2 equations with 2 unknowns
I've been trying to solve a system of 2 equations with 2 unknowns using NSolve. But It's been too slow. I waited for more then an hour without any results.
The code is:
...
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38
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How to treat small numbers in order to gain efficiency and precision in neural network algorithm?
Unfortunately I won't be able to provide a MWE, as it would be too big and complex, and this question will be based on pure semantics, basically (and I understand if this is impossible to answer in ...
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1
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63
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NMinimze cant find points that satisfy constraints
NMinimize cant find solutions for a function which clearly has one. Setting a working precision resulted in some output, however with error messages about tolerance and precision.
Heres my code. The ...
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0
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65
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Numerical Error using compile
I'm trying to compile a function and I'm running into the following error
CompiledFunction::cfne : Numerical error encountered; proceeding with uncompiled evaluation.
I think I have succeeded in ...
0
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1
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113
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Performance improvements using Table and Compile
I'm converting a code from MatLab to Mathematica. It takes MatLab less than a second to compute it while its more than ten minutes in Mathematica. I was hoping to improve the performance.
Here's a ...
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1
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67
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How to make faster of a code containing more iteration point? [closed]
I am trying to evaluate a code of the Power Series Solution method to get the results. Also, the time of evaluation depends on the parameters I am using. When the iteration point is 50, 60, or 80, it ...
1
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2
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166
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How to make faster of a code containing more iteration points?
I am trying to evaluate a code of the Power Series Solution method to get the results. Also, the time of evaluation depends on the parameters I am using. When the iteration point is 50, 60, or 80, it ...
0
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1
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118
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How to minimize numerical error in the code while solving the system of ODEs
I just want to ask in the graph of the code mentioned in the link, while plotting u from {-0.0001,y,0.0001}, the jump is coming because of the numerical error u1-u2. Can anyone please tell me, how to ...
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2
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155
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Finding closed form representations of floating point numbers?
Is there a trick to automatically recognize that ${-0.5771,1.2280}$ are approximately equal to {-EulerGamma, Log[2 + Sqrt[2]]}?
These were obtained by using ...
0
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1
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51
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Proceeding integral or summation calculation with no explicitly designated quantities, but instead with an abstract 'n' quantities
Could someone kindly tell me how to calculate formulas such as integral or summation with no explicitly designated algebra quantities as derivatives or summands, but the abstract ' n' quantities ...
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41
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Nested NIntegrate with Matrix Exponential
I wish to perform a numerical integration which involves a matrix exponential. Here's the following code
...
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1
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79
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a problem in numerical integration in Mathematica
I am trying to numerically compute an integral of the following type in Mathematica. I can show that this integral can be computed analytically. Still, I want to make sure Mathematica can also give me ...
1
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0
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53
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Increase computation speed for nested integral equations
I want to numerically solve these two nested integral equations
$$q(J_0,T)=\int_{-\infty}^{\infty} \frac{1}{\sqrt{2\pi}}e^{-\frac{z^2}{2}}\,\mbox{tanh}^2\left(\frac{z\sqrt{q(J_0,T)}+J_0 m(J_0,T)}{T}\...
0
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0
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35
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Solving system of ODEs dropping one component of general solution
Question:
I want to solve the following system of differential equations:
...
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0
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46
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Identifying the parameter that flips the solution
I have solved a system of ODEs numerically. As the plot shows, the solution SolJx is positive for the parameters I have chosen. However, if you decrease (more ...
0
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0
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88
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Error in numerical integration using Wolfram Mathematica
I hope you are doing well.
I am having serious problems while calculating a numerical integral in Wolfram Mathematica, as the following error messages appear:
1- "Numerical integration converging ...
1
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0
answers
77
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Numerical solution system of ODEs
I want to solve the following system of ODEs with four boundary conditions:
...
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1
answer
173
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How to numerically solve differential equations with singularities?
I wish to solve a differential equation numerically. As an example, I tried solving Hypergeometric differential equation
...
1
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1
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59
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Value given by NIntegrate is double of Integrate function
I am performing a calculation where the result of NIntegrate and Integrate is different. They differ by factor of 2. Can someone tell what is the reason and how to make the NIntegrate value right?,
<...
2
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2
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202
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Solving complex equation numerically
I'm trying to solve the following equation for $z$ for a set of given complex values of $a$ and for fixed $b$ (without providing any initial guess value(s)):
$2^{iz}~\Gamma\left(\dfrac{iz+b}{2}+1\...
3
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2
answers
377
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How can I speed up calculation of the integral?
Is it possible to speed up the calculation of the Kx integral?
...
3
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1
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85
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Why two the same integrals give different values?
Why two the same integrals give different values?
...
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0
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61
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How to solve this nonlinear partial differential equation stably?
I'm trying to solve this PDE with a numeric method. For an approximation, a radius $r$ that is sufficiently large (but not infinity) should be enough. When the coefficient of the initial condition $\...
2
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2
answers
111
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NMaxValue - function is not a real number
I'm trying to use NMaxValue to numerically find maximal values of the function F[z]. The problematic part of my code is as ...
0
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2
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68
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How to find the point where Exclusion starts?
I have two versions of a Plot
...
2
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1
answer
66
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What numerical error is Mathematica doing here and how can I avoid it? [closed]
So I am solving a system of equations in Mathematica:
...
2
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2
answers
149
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How to get correct numerical result without lots of digit precisions?
I am wondering if it is possible to get the correct numerical result without computing with a lot of precisions in expressions.
as a simple example suppose in the middle of some of my numerical code ...
3
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1
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136
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Shooting technique using NDSolve
Here I am attaching my code below. It took all the variable's values, but the graph window was empty. I am not able to recognize, where is the error exactly. Differential equations were also, checked ...
0
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1
answer
66
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Integration is not correct for the expression with a fraction?
What value Px2[16, 4] or N[Px22[16, 4]] is correct?
...
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0
answers
33
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How do I prevent, or get rid of the <code>Abs^\[Prime]</code> in the output of a partial of a Normalize[vector]? 12.0.0 for Microsoft Windows [duplicate]
12.0.0 for Microsoft Windows
How do I prevent, or get rid of the Abs^[Prime] in the output of a partial of a Normalize[vector]?
The code below shows the problematic ...
5
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1
answer
138
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Incorrect answer zero where correct answer is very large (precision issue)
Define a function F as follows:
F[α_, x_] =
N[Exp[x/2] Abs[Gamma[α/2 + I x /(2 Pi)]]^2, 10];
It is a product of two terms. ...
1
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1
answer
103
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Shooting technique [closed]
Here is my code, I am trying to plot the graph of the differential equation, But output graph is an empty window. can anyone please help in getting the graphs. This equation is a modified bessel ...
0
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0
answers
118
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How to increase the precision of numerical derivatives?
I need to make sure about precision of numerical derivatives in my calculations. I use finite element method to obtain a wave function, then I take derivatives of this numerical wave function to get ...
0
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1
answer
49
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Why does an error occur in one case, but not in the other, and how to fix it?
Why do errors appear for this Kx[11, 15] when this Kx[11, 14] is considered without error? How to fix it?
...
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2
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128
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Finding numerically roots of equation over region
I'm trying to solve the following numerical problem:
I have a function of 2 variables in some rectangular region, the function is computed numerically with some moderate time cost (solution of linear ...
1
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2
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138
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Why does NDSolveValues give different results?
I'm trying to solve this differential equation to obtain the density matrix elements $\rho_{22}$.
$$\frac{d\rho}{dt}=-i\Big(H_{0}(t)\rho(t)-\rho(t)H^{\dagger}_{0}(t)\Big)$$,
for non-Hermitian ...