Questions on the use of numerical functions NIntegrate and NDSolve.

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2answers
83 views

NIntegrate Error

I am trying to solve this expression with the function NIntegrate: ...
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2answers
94 views

Numerical Integration

I have used the following code to evaluate an integral (val) numerically ...
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1answer
131 views

Plotting an function defined by an integral [closed]

How can I plot a function defined by an integral. More specific, I have the following equation: $$ T = ...
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2answers
136 views

Integral with unreliable result

I want to calculate $\int_R^1 \sqrt{r} |\cos((k+\frac{1}{2})\pi r)|dr $ and I get a result from Mathematica. Then I try to check the result putting the value of $k$ and $R$, (k=1 and R=0.5) in the ...
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1answer
70 views

Compute integral symbolically

I want to compute the following integral: ...
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1answer
163 views

Numerical solution of the hyperbolic equation

I am trying to solve the following hyperbolic equation with given boundary conditions: I choose as initial condition $u=1$, and evolve the above hyperbolic equation until reaching a stationary ...
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1answer
70 views

Numerical integration with purely numerical integrand

I'm trying to perform a numerical integral with an integrand that should not be manipulated with any symbolic preprocessing whatsoever. Consider the following simple test : ...
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1answer
42 views

Calculate Integral with cos [closed]

Integrate[ (Pi/4 - x/2) cos (n *x), {x, 0, Pi}] This doesnt give me desired results .n is natural 1,2,3,4,5... I want to get something like ...
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1answer
148 views

How to solve this integral equation?

I am trying to solve for x the integral equation : ...
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1answer
223 views

Infinite expression 1/0.^(1/4) encountered in NDSolve

I am trying to solve very simple system of coupled differential equations using the NDSolve function, but I am getting ...
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2answers
356 views

Double integral with variable in the limits

I'm trying to solve this integral: $$ ...
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1answer
371 views

How to use NIntegrate in a function using parameters from a list

I would like to use NIntegrate in a function with some parameters from a list. I simplified my problem for this forum. The list of parameters is as follows: ...
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2answers
204 views

NDSolve boundary query / Extracting values from solution

I have a function $O_{2}$ with boundary conditions $O_{2}(r_{o}) = p_{o} $ and $O_{2}(g) = O_{2}'(g) = 0$. I plot it using the solver code below; ...
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2answers
161 views

NIntegrate using Boole doesn't work

This doesn't want to work for me - I don't know why not. It usually gives me 0, but sometimes also a different number. I know it should be a small, non-zero number. ...
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1answer
501 views

NIntegrate & non-numerical values

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. How can I ...
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1answer
1k views

Nested Nintegrate - two variable limits of integral

This is, so to say, the next part of the question: Nested NIntegrate - NIntegrate::inum: - error Now I define three functions: ...
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1answer
394 views

Nested NIntegrate problem

So I've been trying to evaluate the following integral in Mathematica 8.0 Student version: ...
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2answers
79 views

Multidimensional Numeric Integration

I can't manage to calculate numerically the following multidimensional integral: ...
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1answer
40 views

NdSolve problem :NDSolve::ndode: Input is not an ordinary differential equation

I am new to Mathematica. I am working on solving the following different equations numerically written in the code as below. Not so sure about the boundary values that depends on R (M(0)=0, n(1)=0) ...
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1answer
58 views

Numerical integration and plotting

New to Mathematica, and trying to numerically evaluate two integrals: ...
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1answer
85 views

NIntegrate vs. summation

I' m interesting in distributions of points on sphere, plane figures etc. Especially for small number of points: 1, 3, 7, ... It seems that good criterion for uniformity of distribution is some ...
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1answer
63 views

Integration does not give real value

The code below must be obvious. We are trying to integrate a complicated function from 0 to 1. ...
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1answer
34 views

Problems using a complicated function within a LogLinearPlot [duplicate]

my problem is that I have a rather large function which I'm trying to plot, which looks something like this: ...
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2answers
76 views

NIntegrate and Integrate of a Spherical Bessel function

I am trying to integrate over a spherical bessel function. I have used both the Integrate and NIntegrate functions in Mathematica but the values given by each do not match. Any reason why this ...
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1answer
51 views

Integral for piecewise function inconsistent with the usual way

I have the following piecewise function: ...
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1answer
71 views

How to ensure efficient order of operations for rules, slots, substitutions?

I need to calculate several functionals Q[[t]] of a pdf f[x]. ...
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1answer
64 views

NIntegrate with units: unable to determine the units of quanitites that appear in the input

I want to integrate Planck's law of radiation in a certain wavelength intervall with units. I define some constants: ...
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1answer
90 views

NIntegrate:eincr error

I am trying to solve this expression in Mathematica with the function NIntegrate: ...
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1answer
57 views

Using ImplicitRegion to define an ellipse around Multinormal distribution for integration

I have both a 2D 'MultinormalDistribution', and also a single xy point, and I would like to be able to calculate the probability of this point (given the multinormal distribution) and also plot an ...
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1answer
624 views

wolfram mathematica intersection of two surfaces [duplicate]

I use wolfram mathematica. There is a function of two variables which defines the surface z = f(x,y), the second surface is defined as z = const. How to find the line of intersection of these two ...
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1answer
136 views

Help using NIntegrate

I need some help with NIntegrate. I pasted the code that I wrote below; I know that up to "de" is correct. What I would like to do is NIntegrate de w.r.t phi{0,0.1} and curlE{-10,10}. The final ...
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1answer
180 views

Numerical integration of two variable function

The aim is to calculate the definite integral of the function $f$ of the form $$f(x,t) \;\;\;\; x \in [0, \infty ) \;\;, \;\;t \in [t_0,T]$$ numerically. For example consider the function below $$f = ...
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1answer
155 views

Integrand evaluating to non-numerical values

I have solved a system of equations using NDSolve just fine. From there, I can plot the solutions $u(x)$ and $v(x)$, as well as its derivatives, just fine. But, when I want to evaluate the energy ...
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1answer
86 views

How can I fix my code so NIntegrate doesn't produce error message?

I get this error when trying to integrate a seemingly simple expression: ...
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1answer
135 views

NDSolve with arrays and Tables of Equations and WhenEvent

I've been toying around with NDSolve for a while, and read through the website. By doing so I discovered that I could use it for vectors and arrays with much pleasure. So I wanted to write a simple ...
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1answer
118 views

Multiple NIntegral with singularity

I need to compute the following integral FF[0]. When evaluating FF[0] Mathematica simply takes too much time. The problem may ...
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1answer
217 views

Initial and boundary value errors

NDSolve::ivone: Boundary values may only be specified for one independent variable. Initial values may only be specified at one value of the other independent variable. >> I keep getting this, ...
0
votes
3answers
327 views

Solving an Integral Numerically

I have been trying to solve the integral equation below, but cant seem to find a way out of this. Can someone please help me out with suggestion? $f(t)=\int_0^{\infty}\frac{K_1a(t)}{a(t)+K_2}\,dt$ ...
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1answer
273 views

Using NDSolve for three variables as function of time

I want to be able to plot z, and r. Should I be using DSolve, NDSolve or something else? I've tried to clear it up a bit Thanks, Will ...
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1answer
201 views

How to improve the performance of this code

I have implemented a code in Mathematica 9 to simulate a scattering problem, and I got really disappointed about its performance when compared to Matlab. Since I am a newbie in Mathematica, would ...
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1answer
101 views

Transformation of the NDSolve result into new dependent variables

I have solved a set of coupled differential equations and now I need to convert them into different dependent variables and sketch their trajectories. Here is the code I have written so far: ...
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1answer
329 views

Fitting a Function With a Numerical Integral [duplicate]

I am having trouble using FindFit with the following function. ...
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1answer
166 views

PDE Solving in mathematica

I'd like to ask how I might go about solving this equation: $\frac{\partial Ci}{\partial t} + \frac{1}{r^2}\frac{\partial (r^2 Ci)}{\partial r} = D\frac{1}{r^2}\frac{\partial}{\partial ...
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1answer
674 views

Syntax question regarding Triple Integrals in Mathematica

Integrate[1, {z, 0, 5}, {x, -Sqrt[ 9 - y^2], Sqrt[ 9 - y^2]} , {y, -3, 3}] 60 Sqrt[9 - y^2] How comes I am not getting a number for my final answer? This ...
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1answer
128 views

Order of evaluation in nested expression

I am trying to make a function that works as follows: Integrate 1 for all t in the interval $ [0,1] $ such that the first element of function vstar is positive. ...
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2answers
590 views

Plot of a function which includes numerical integrals

I want to make a 3D plot of two variable i1 and b1. The dependent variable results from a pay-off function ...
0
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1answer
187 views

find derivative with defined function

s[a_, b_] := NDSolve[{y''[x] == y[x] Cos[x + y[x]], y[0] == a, y'[0] == 1}, y, {x,0, b}] I need to find the minimal of $\int _1^by[x]^2$ in the region ...
0
votes
1answer
635 views

Solving coupled eigenvalue differential equations

I am trying to solve an equation of the form as follows $\left(\begin{array}{cc} -\frac{\hbar^{2}}{2m}\frac{\delta^{2}}{\delta z^{2}}+\sin^{2}\left(z\right) & z\\ z & ...