Linked Questions

2 votes
1 answer
297 views

Computing the coefficients for Gaussian integral [duplicate]

I wrote a small script to find the Gaussian integral points and weights: ...
Kattern's user avatar
  • 2,571
10 votes
2 answers
1k views

Fredholm Integral Equation of the 2nd Kind with a Singular Difference Kernel

After reviewing the literature, I could not find an analytic solution to the equation $$\int^{1}_{0}dx\frac{f(x)}{|x-y|^{2/3}}=cf(y)$$ for $f(y)$, where $c$ is a constant and $y\in[0,1]$. I'm ...
Asaf Miron's user avatar
6 votes
3 answers
1k views

Why Gauss-Legendre Quadrature should keep the number of integral points less than about 50?

I wanted to use Gauss-Legendre Quadrature to calculate an integral as follows: When n=10 and some other number(except odd numbers),the numerical result is the same as theoretical result. ...
Quere's user avatar
  • 93
9 votes
1 answer
1k views

Two-dimensional catenary in Mathematica

I'm working in Mathematica to plot a 2-d catenary in Euclidean space according to this Math Stack Exchange Link, specified with a square Dirichlet boundary condition. Here's what I've coded using ...
Brandon's user avatar
  • 93
2 votes
2 answers
929 views

Why Gauss-Legendre rule gives wrong result for piecewise polynomial function?

I implemented the Gauss-Legendre rule as follows: $$\int_0^1f(x)dx=\frac 1 2 \int_{-1}^1f(\frac{1+x}{2})dx=\sum_{i=0}^{4}A_if(\frac{1+x_i}{2})$$ ...
xyz's user avatar
  • 625
8 votes
2 answers
579 views

Is it possible to take a numerical (integral) average of the dependent variable, within NDSolve, at each iteration?

tl;dr: want to integrate (average) the dependent variable within NDSolve. I am currently trying to implement a basic diffusion-advection equation for a reactant, A. The species is converted between A ...
rbean's user avatar
  • 83
6 votes
2 answers
348 views

How do I improve the style, efficiency, and versatility of this code?

I have a math problem that I have solved analytically. I now want to generate a number of graphs based on different parameter values. My problem is threefold: It takes a couple of minutes to produce ...
user152497's user avatar
8 votes
1 answer
1k 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 <...
Enter's user avatar
  • 1,229
3 votes
1 answer
1k views

NDSolve: Couple PDE and ODE involving integral

I am trying to numerically solve an equation with NDSolve, where there is a ODE coupled to a PDE, like the following: ...
Lufu's user avatar
  • 51
3 votes
2 answers
391 views

Need help to speed up the Gaussian quadrature

I am trying to compute the $L_2$-norm of the solution $y(z,t)$ of a PDE with Gauss quadrature using the following code, where $z$ is space position and $t$ is time, then to construct it as a function ...
Nobody's user avatar
  • 823
2 votes
1 answer
1k views

gaussian integration

I'm new on Mathematica and I am an engeneer with only a little base of numerical computation. I have to integrate a trigonometrical function numerically with a Gauss integration. The function is: <...
diana's user avatar
  • 65
1 vote
1 answer
941 views

NonlinearModelFit runs too slow when fitting data to a function that does multiple numerical integrations

I have a function of several parameters defined in a module which does multiple numerical integrations. Then I try to fit that function to some sample data via with ...
ILLG's user avatar
  • 11
0 votes
2 answers
434 views

Accuracy and WorkingPrecision

Observe that ...
Chen Stats Yu's user avatar
4 votes
1 answer
251 views

A Trial Boundary Element Approach to Solving Integral Equation

I am trying to numerically solve an integral equation in Starfield and Crouch textbook (Boundary Element Methods in Solid Mechanics: With Applications in Rock Mechanics and Geological Engineering), ...
D. Andrew's user avatar
  • 423
3 votes
1 answer
367 views

How to handle this constant-interval integral in ODE?

The problem is to solve a system of nonlinear equations with a definite integral. $Q_i(x), i=1,2,3, x \in [-\text{max},\text{max}]$ \begin{align*} a_iQ_i''(x)-b_i(\vec{Q})-d_i\int_{-\text{max}}^{\text{...
xiaohuamao's user avatar
  • 4,728

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