# Tagged Questions

Questions on the use of numerical functions NIntegrate and NDSolve.

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### 2d numerical integration

I'm trying to get a numerical solution for a double integral: ...
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### Integration of a function of interpolating functions

I need to calculate the integral of a function of interpolating functions. Being more specific, the function I want to integrate is the following ...
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### NDSolve for complex variables

I am trying to simulate a multiple pendulum system with damping as follows: ...
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### Why MMA is not able to solve this problem? [on hold]

I am running these following code in Mathematica. But, MMA does not output anything. It is giving me an message as "The integrand .... has evaluated to non-numerical values for all sampling points in ...
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### Mathematica9: NDSolve slows down after repeated calls

Bug introduced in 9.0 or earlier and persisting through 10.4.1 or later I have noted that in Mathematica 9 my code, which involves a lot of calls to NDSolve, ...
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### ParametricPlot3D shows an empty box

I'm trying to visualize numerical solution of 4 differential equations (these are the coordinates of a wave function in a quantum mechanical system): ...
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### NDSolve giving the wrong solution?

I'm considering the non-linear second order ODE DE $=0$, with DE given by ...
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### Numerical integration and interpolation with free parameters [closed]

I hope you'll be able to give me a hand on my question, I'm stuck and don't know how to make it work. First of all, I have a table of data pairs (x,f): ...
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### What method does NIntegrate use by default?

There is a variety of algorithms for performing numerical integration (See wiki). What method does NIntegrate use by default? I looked at the documentation page ...
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I just learned about the Inverse Symbolic Calculator and it seems like a very useful tool. For example, to find an analytic solution to $$\int_0^{\infty } \frac{1-e^{-x} (x+1)}{\left(e^x-1\right) \... 1answer 101 views ### Understanding difference between NIntegrate result and home-cooked Simpson's rule In this question I am asking about the different results I get between NIntegrate-ing a function of two variables vs. "doing it myself" with my own implementation ... 0answers 30 views ### Difference between using NIntegrate and Integrate inside NDSolve? The differential equation I am considering depends on an integral, which I would like to solve with NIntegrate (since it will gets more complicated and thus I have to use NIntegrate later). My code ... 5answers 3k views ### How to speed up the plot of NIntegrate? Here is a toy example: f[t_] := NIntegrate[Sin[x], {x, 0, t}]; Plot[f[t], {t, 0, 10}] // Timing Even such a simple example will take 2.8 seconds on my computer. ... 1answer 67 views ### Mathematica will not run Arnoldi method while using NIntegrate This is simplified version of my real code: ... 1answer 88 views ### Numerical integral of finite valued function over finite integral fails with NIntegrate::inumri I have the following (simplified) integral: ... 0answers 52 views ### Double Integral with NDSolve! I have fivefold multiple integral and I wanted a speed calculations.I came across on this Question and had already begun the problems. Here is a toy example with simple double integral: ... 6answers 878 views ### Integrate gives wrong results Integrate[a/(Sin[t]^2 + a^2), {t, 0, 2 Pi}]$$\int_0^{2 \pi } \frac{a}{a^2+\sin ^2(t)} \, dt$$gives 0 This cannot be true. What is going on? If I insert a ... 2answers 66 views ### In NDSolve, how to involve in the odes a integration function that depends on ode functions and can't be analytically integrated? I think it would be better to use this simple code to explain my questions: ... 2answers 122 views ### NIntegrate evaluates its 1st argument while it has the attribute HoldAll? NIntegrate owns the attribute HoldAll: Attributes@NIntegrate (* {HoldAll, Protected} *) ... 0answers 22 views ### Launching specific remote kernels in parallel For some reason I found that my numerical integration runs much faster on Mathematica 9 than on Mathematica 10. Since I sent my calculation to a cluster with 24 cores with the following command <... 3answers 266 views ### NIntegrate and Integrate of a Spherical Bessel function I am trying to integrate a spherical Bessel function. I have used both the Integrate and NIntegrate functions in Mathematica but ... 2answers 119 views ### Why NIntegrate is badly-behaved on J_{\frac{9}{2}}(x) by default? A friend of mine showed me this example: Plot[BesselJ[9/2, x], {x, 0, 1}, PlotLabel -> Style["The integrand seems to be simple", 14]] ... 1answer 522 views ### How can I invoke the solution of NDSolve to determine a parameter in my equation just inside NDSlove? I am trying to solve a differential equation by NDSlove for h(x,t). It reads$$h_t=h_{xx}-V_h-\lambda(t) where $V_h$ is a given function of $h(x,t)$ denoted by <...
I'm trying to find an expression that, given $x$, $y$, and $R$, gives the indefinite 2D integral of a function at the circle centered on $(x_0, y_0)$ with radius $R$. With $g$ as defined below, I'd ...