# Tagged Questions

Questions on the use of numerical functions NIntegrate and NDSolve.

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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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### 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 ...
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### How to prevent tiny complex errors in Integrate?

Integrate is adding a tiny imaginary error to an easy result. Why? And how can I stop it? ...
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### How to obtain numerical answer for equation containing integration

Could some one tell me how to obtain numerical value of $a$ and $b$ from equations below: $$\frac{1+exp(b)}{1+exp(0.9a+b)}=0.95$$ $$\int_{0}^{\infty} \frac{1+exp(b)}{1+exp(a x+b)}=1$$
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### Finding the true expectation

I have the density function and I want to determine its expected value ...
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### Numerical integration: complicated 2D integral seems to be poorly estimated

In the course of some physics research I've been working on, a very annoying integral has appeared that I'm having difficulty evaluating numerically. Any help you could offer would be greatly ...
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### Numerical Integration/Function

I have a problem with a function defined numerically through an integral of the form: ...
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### What means the definition F[t_?NumericQ] :=…? [duplicate]

I've come along a function defined in this way: F[t_?NumericQ] := NDSolve[{-u''[x] - u[x]/x == -t^2 u[x], u[x0] == x0, u'[x0] == 1}, u, {x, x0, x1}] What does ...
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### Runge-Kutta Butcher tables

I like to have the Butcher's table for Explicit (or implicit as well) Runge-Kutta method of a fixed order. I do not understand reading http://blog.wolframalpha.com/2013/09/10/numerical-methods-runge-...
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### NDSolve not able to solve a system of differential equations

Here are some basic equations ...
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### Is there any way to solve this convex-concave like optimization problem?

This is a bit of a non-standard way of asking a question perhaps but I couldnt even think of writing any code about the following optimization problem. I wonder if it could be at all solvable and if ...
I want to evaluate the differential entropy according to here $$h(X) = - \int f(x) \log{f(x)} dx$$ where $f$ is the probability density function. Lets create some test data (normal distribution): <...