Tagged Questions

Questions on the use of numerical functions NIntegrate and NDSolve.

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Numerical solution of IVP for linear ODE with variable coefficient runs wild soon

Cross posted in scicomp.SE. A friend of mine showed me this initial value problem (IVP) for a linear ordinary differential equation (ODE) with variable coefficient: $$y''(x)=\left(x^2-1\right) y(x)$$...
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Volume by NIntegrate gives zero

I want to Integrate the following expressions for different p < n and 2 < n with p and n both natural numbers: ...
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How to plot the solution of a Partial Differential Equation?

My attempt. I need to solve numerically the Complex Ginzburg-Laudau Equation (CGLE): $$\frac{\partial A}{\partial t}=\epsilon A-(1+i\beta)|A|^2A+(1+i\alpha)\nabla^2A$$ I'm using a uniform initial ...
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Plot a numerical integration as a function of a variable

Suppose we have a function that is hard to evaluate analytically but a numerical estimate suffices. For example consider the $f(x,\Lambda) = \Lambda\cdot \sin(x)$ where $\Lambda$ is some parameter I ...
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Solving for the limits of an integral

I am trying to get Mathematica to solve for the symmetric limits of an integral of a Square Wave. ...
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NdSolve problem :NDSolve::ndode: Input is not an ordinary differential equation

I am new to Mathematica. I am working on solving the following different equations numerically written in the code as below. Not so sure about the boundary values that depends on R (M(0)=0, n(1)=0) ...
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Enforcing WorkingPrecision in NIntegrate

I have a very complicated 2D integral that I need to calculate repeatedly, and I'm trying to speed it up a bit, since at the moment it's taking a couple of days to complete. One thing I've noticed is ...
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NIntegrate vs. summation

I' m interesting in distributions of points on sphere, plane figures etc. Especially for small number of points: 1, 3, 7, ... It seems that good criterion for uniformity of distribution is some ...
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Simple integration with assumption

I would like to evaluate the following simple expression NIntegrate[Re[Exp[I*Omega*t]], {t, 0, 2 Pi}] for Omega real, but ...
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Implicit region misses subset?

Context I am interested in integrating a 2D function over lines defined implicitely Attempt Let me just start by integrating the identify on such sets of lines which a defined using ...
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Numerical integration's speed

Consider this numerical integration of Bessel function: Do[NIntegrate[BesselJ[2, x], {x, 0, 10000}], {i, 1, 100}] // AbsoluteTiming {4.033403, Null} This is ...
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Slow evaluation of NIntegrate when used as a pure function

I asked a perhaps related question here. Here is my code in below. The goal is that to define a function which must be integrated numerically. The function itself first is calculated over different ...
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Numerical integration and plotting

New to Mathematica, and trying to numerically evaluate two integrals: ...
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Slow exponential evaluation over lists

This question,which is still unanswered, might be relevant because it involves NIntegrate over lists and it also has Exp. In ...
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A problem about NIntegrate the smaller eigenvalue for a matrix

Define a matrix and a function as ...
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Quantum Physics question [closed]

I'm not sure if anyone here would be able to help me. But if you know a more appropriate place where I could ask for help, please let me know. So here's the question: And here's my attempt at ...
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Initial Step Size for NIntegrate

I am using Mathematica to numerically integrate a numerically-defined function (from an interpolation and data). This function has a sequence of somewhat unevenly spaced sharp peaks which dominate ...
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How to force Mathematica to throw an error for NIntegrate

Consider this: NIntegrate[BesselJ[2, x], {x, 0, Infinity}] 0.9999999999904574 This is the correct answer. Now: ...
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Strange Behaviour of NIntegrate

I found some of the values remained unevaluated using the following code Table[NIntegrate[Sin[i x]/((2^x + 1) (Sin[x])), {x, -Pi/2, Pi/2}], {i,70, 90}] Pick them ...
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Wolfram Alpha will calculate this definite integral but Mathematica won't

I'm trying to compute a definite integral of the form $$\int_{0.2}^{0.5} \frac{1}{(1 - y)y^2\sqrt{0.5 - y^2 + y^3}}$$ in Mathematica. WolframAlpha will calculate this but Mathematica only outputs the ...