# Questions tagged [numerical-integration]

Questions on the use of numerical functions NIntegrate and NDSolve.

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### Problem with a DAE and DiscreteVariables (II)

I continue with a DAE problem similar to another one posted here some days ago. @bbgodfrey offered a solution for the DiscreteVariables problem but now I have a ...
1 vote
102 views

### Solution on nonlinear pde with intial condtion

It produces an error. please suggest an alternative solution to the above-coupled pde problem. ...
1 vote
84 views

### Solving system of equations including numerical integrals over region

I am dealing with the resolution of a concrete beam. Simply put, it is an equilibrium of horizontal forces and moments. Let's first define some parameters : ...
1 vote
46 views

### How to solve the error information in numerical integration and solve Sp?

How to solve the error information in numerical integration and solve Sp? The codes are as follows: ...
103 views

40 views

### Cannot fit data due to NIntegrate errors

Here is the data I am trying to fit ...
137 views

### How to remove error in NIntegrate

I want to solev NIntegrate in two dimension. But when i run the code i got Throw::nocatch: Uncaught Throw[-HolonomicDifferentialRootReduceDumpy[NIntegrateLevinRuleDumpx]+(...
65 views

### I want to solve Integrate [duplicate]

I am wondering why I am receiving the message "The integrand ... has evaluated to non-numerical values for all sampling points in the region ..." for a particular calculation I am running. ...
1 vote
83 views

### Avoid imaginary result FindRoot

I have a code where I'm using FindRoot for the equation toroottp. I plug in some sample values on ...
1 vote
44 views

### Looking for an appropriate method of NDSolve for dynamical system

I am dealing with the numerical solutions of a variety of dynamical systems with integrals of motion. As the example, let me consider the Kuramoto model, which equations of motion are ...
54 views

### Integration over an implicit region

A question asks me to calculate the following integral using NIntegrate: Calculate the double integral ... where D is the area bounded by the four lines ... With ...
81 views

### Getting negative value instead of a positive value [closed]

The function is ...
60 views

### Getting a wrong plot after NIntegration

I am trying to plot this function numerically. R2T = ...
117 views

### Speeding up Boussinesq equations solving?

I am working on Boussinesq equation. The notebook can run perfectly for only 0.6 steps and then the calculation starts running slowly after 0.7. All boundary conditions seemed fine. I am unsure if I ...
83 views

### Problem with NIntegrate a solution of NDSolve

I'm having trouble making a function that uses the result of NDSolve: ...
2k views

### Can Mathematica calculate this elliptic, triple integral?

Integrate[(4 a b/Pi) (a^2 + b^2 - 2 a b Cos[c])^(1/2), {a, 0, 1}, {b, 0, 1}, {c, 0, Pi}] I'm using basic plan, it gives me the result like that. The ...
76 views

### BVP with 2nd order coupled ODEs

I get the following error messages: Infinite expression 1/0. encountered. Indeterminate expression 0.\ ComplexInfinity encountered. Encountered non-numerical value for a derivative at s == 0.1 ...
44 views

### Why does Mathematica not know some integrals diverge?

I want to analyse the convergence of some complicated 1d integrals that may have divergences at $x=0$, similarly to the harmonic integral $\int_0^a 1/x \ \mathbb{d} x$, which I know is divergent. When ...
62 views

### NDSolve: there are more variables than equations, underdet

I am working on using NDSolve to solve coupled ODE. The following is the coupled equations. It works fine for sever orders. I used table to generate like 962 couple variables and equations, where the ...
162 views

### Numerical solution of an advance-delay ODE with multiple advances and delays

I am trying to solve a differential equation of the form ...
61 views

### I am unable to plot 3D graph of integral function

I am not able to solve this integral ...
1 vote
56 views

### How to make the NIntegate of two variables as efficient as possible

I asked my question here (Multivariable NIntegrate gives different value if I integrate it separately), I think the best way to get help is by putting the original code here. So, my question is how ...
47 views

### NDSolve overdetermined but I can't see how

Edit: partial answer This confuses me but it is due to some behaviour of pattern matching which just seems wrong to me. An example of the behaviour ...
1 vote
98 views

### Multivariable NIntegrate gives different value if I integrate it separately

I have a double variable integral, so I can define a function which is the integration of the other variable, and finally, I integrate the other variable. here is the code: ...
74 views

### Too big error of numerical integrate

I want to do some numerical integrate with Mathematica, but the results are very different from others' result calculated by C code. Here is my code: ...
103 views

### Inconsistent results between NIntegrate and Integrate

I get these inconsistent results What is going wrong? Fast oscillating terms? Small exponential factors? But then, why the result seems to toggle between values 1 and 2, rather than being a real ...
49 views

### Solution of NDSolve evaluates pointwise, but won't plot (possibly due to issue with FindRoot and replacement rules)

I'm trying to solve a pair of uncoupled differential equations using NDSolve, where the initial conditions are determined by FindRoot. Here's the relevant section of the code, including error message. ...
1 vote
106 views

### Integration of accelerometer data to x-y-z position [closed]

Hi I have a list of accelerometer data, in their xyz acceleration values. May I ask how can I integrate these data to get to the position in their xyz angle, assuming the initial velocity is zero and ...
49 views

### NIntegrate can't integrate function but work fine with the expression [closed]

I have a function called psi0 that looks like this: psi0 := E^(-(x - 10)^2/10) and I'm trying to integrate it numerically from 0 to a variable L. However, I keep ...
69 views

### Problem with NIntegrate and more general problems with NDSolve

I'm new to Mathematica and I'm receiving little help for a (to me) quite difficult problem I'm trying to solve. I want to solve logarithmic Boltzmann equation for abundance of dark matter. I'm having ...
1 vote
58 views

### Choosing spatial direction in Method of Lines

Edit:The temporal variable can be set using Method -> {"PDEDiscretization" -> {"MethodOfLines","TemporalVariable" -> t}} ...
249 views

### Poincare section for a perturbed string

I am trying to find the Poincare section of a perturbed string in a gravitational background with a magnetic field. The plots that I am trying to reproduce are from this paper (page 11). The code that ...
63 views

### Non Linear System of Diferential Equations with periodic function

I am programming a system of differential equations consisting of 3 cell populations; Normal cells N, Tumor cells T and chemotherapy treatment Q, when a function q is constant. The system is as ...
134 views

### Numerical integration of highly oscillating function

I want to Numerically integrate the following function ...
41 views

### How to do double numerical integration one of the variables integrate to another one

Here I have an express with two variables like ...
How can I use Mathematica to solve the following higher order and nonlinear fractional equation? \partial_t u(t,x) +\partial_x(u^k(t,x)\partial_x(-\Delta)^su(t,x)) = f(t,x) \quad t >0, \ x \in (\...