# Questions tagged [numerical-integration]

Questions on the use of numerical functions NIntegrate and NDSolve.

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### Trouble implementing switching hybrid system with NDSolve

I'm trying to use NDSolve to simulate a hybrid nonlinear system that switches between different linear behaviors based on states and inputs (i.e. switching from one linear behavior to another) which ...
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### Plotting an integral with solving for a specific constant [closed]

Given an Integral I(t) which is a function of a constant tc, this constant is determined with the condition I(tc)=0, how can I add this condition?
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### Numerical Integration without giving all values

Is there a way to solve expressions numerically, while keeping other variables. For example, I want to Integrate the expression below for $\theta p,\theta q$ while keeping other things as it is. The ...
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### Method to make this complicated integration from interpolating function? [closed]

Hello I want to do this integral Mu[Psi_, R_] = Integrate[ D[Integrate[Rp f[Psip, Rp]/Sqrt[R^2 - Rp^2], {Rp, 0, R}], R]/ Sqrt[Psi - Psip], {Psip, Psi0, Psi}] ...
1 vote
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### How to solve the following integrodifferential equation by generic approach?

Consider the following equation: $$\frac{\partial f}{\partial t} - p H(t)\frac{\partial f}{\partial p} = \mathcal{I}[p,t], \tag 1$$ Here, f = f[p,t], with p being ...
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### 2D and 3D versions of GaussianQuadratureWeights?

The package Get["NumericalDifferentialEquationAnalysis"]; provides a very useful function ...
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### Integration by Numerical Methods

I have a big expression, ...
1 vote
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### Imaginary Result on NDSolve+NIntegrate

I posted the same question in the Physics StackExchange, wondering if it is physics problem. I haven't received any answers, so I am posting in Mathematica StackExchange to see if it is programming ...
1 vote
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### Trouble evaluating the following integral

I am having trouble performing the following integration which comes from a larger function (let me know if I inputted the code wrong from Mathematica so I can fix it!) and even with assumptions, ...
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### How to solve this integral equation numerically?

I am encountering difficulties while trying to numerically solve an equation in Mathematica that involves an unknown function and an integral. Specifically, the equation takes the form of \begin{...
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### Step problem in NDSolve with FixedStep method

We want to solve a set of ODEs with fixed step, whose size is 1/1000, the related codes are given in the following. The parameters are given by ...
1 vote
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### Implementation of SINC filter using Integrate results in incorrect output

Bug introduced in 6.0, persisting through 13.3.1. This is SINC filter, integrate $|H|^2$ from $-\pi/2$ to $\pi/2$. MMA CODE, Result = 7.27956e-12 ...
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### Plotting function defined via NIntegrate is too slow

I have the following functions as solutions of a system of differential equations (for calculation, I used ParametricNDSolveValue) ...
135 views

### Galactic rotation speed and density research

Rotation speed of Milky Way looks like this until about 25 kpc I know the following points to describe this curve ...
68 views

### How to make NIntegrate with large integration limit?

I try to double integrate this equation with respect to $b$ and $f$ ...
142 views

### Numerical Galerkin method with parametrized interpolation function

modified Here I try to realize a numerical fit (Galerkin method) using parametrized Interpolation function to fit examplary Exp[x] in a given grid. So far I tried <...
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### NDSolve returns stiff problem and forces extrapolation which gives unreasonable result

I am trying to solve a first order ODE using ParametricNDSolve for getting particle trajectory in a flow around an obstacle. I got an error message that "At t == 221.96028149270003, step size is ...
1 vote
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### Graph lines do not show dashes [closed]

I have the following code of an iteration: ...
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### Set of differential equations with trigonometric functions and a derivative squared

I've been trying to solve a set of differential equations that involve the square of a derivative, similar to another post I made here, and trigonometric functions, as seen here \begin{equation} \frac{...
98 views

### Evaluation and plot the result of NIntegrate obtained from NDSolve

First I solved coupled ODE using NDSolve. Now I want to integrate the expression (p''' - ((1.0/k)*p'') + (beta*m*m*s) with respect to the parameter ...
444 views

### Solving coupled differential equations involving the square of the derivative

I want to solve the following system of coupled differential equations in order to obtain particle trajectories: \begin{equation} \frac{dt}{ds} = (E-y\, p_t)y \end{equation} \begin{equation} \...
305 views

### Volume of Region Contained by 3D Data Points

I have a dataset consisting of (x,y,z) data that describe a surface, and I need to find the volume of the region bounded by that surface. The data do not follow any mathematical equation, but the ...