Questions about approaches for simulating physical systems or phenomena by building from related understanding and basic principles.

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0answers
36 views

Recycle boundary condition

I'm having the following issue that can not find a solution , by using this boundary condition u[0, t] == 2 u[1, t] that Mathematica does not understand, someone ...
0
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2answers
78 views

Determine the initial speed and launch angle of a projectile from its trajectory

I have the coordinates {x,y} needed to plot the trajectory of a projectile, which are given below: ...
0
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0answers
41 views

Stochastic proccess in mathematica using itofunction and different processes(Bernoulli and weiner)

$ds(t)=K B (t) s( t)+\alpha (\mu -s (t))+\sigma dw(t)$ Where $(\alpha ,\mu ,K,B t,\sigma ,w)$ are in order(reversion factor, mean,Random N~(0,1),BernoulliProcess(0.008), Volatility,Weiner process) ...
3
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0answers
50 views

How to do multi-agent modeling?

There are tons of examples here: http://demonstrations.wolfram.com/topic.html?topic=multi-agent+modeling&limit=20 But I been unable to find a good guide explaining what is the recommended ...
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1answer
127 views

Phase Portrait to Differential Equation [closed]

I posted this question on Math.SE and have received a satisfactory answer in the context of that website. I am re-posting it here to get input from Mathematica users. Why would I receive a different ...
1
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1answer
54 views

Generate a simulated covariance matrix

I am working on a problem where one of the input variables is the level of covariance between the entries in a particular matrix. To simulate this problem in Mathematica, I will need to feed my code ...
1
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1answer
103 views

How to use a random number generator as an independent variable in an existing model?

I am relatively new to Mathematica and I need some help regarding how to create a random number generator to be used as an independent variable for a model my group has been working on. Following is ...
3
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2answers
131 views

Comparison between numerical solution of nonlinear ode and nonlinear ode of second order

Background Let's consider the following initial value problem for nonlinear system $$ \begin{cases} E' &=& 1 - n_e, \\ n_e' &=& -8\,n_e\,E, \end{cases} \tag{1} $$ with the following ...
4
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2answers
167 views

FindFit and NMinimize to fit a parametric model (minimize the distance of two curves)

I am trying to find a fit to the cumulative distribution of a set of points using FindFit or NMinimize. In particular, I would like to find the parameters of the cdf of the Beta Distribution that ...
0
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0answers
67 views

Help needed, building a trajectory model [duplicate]

I'm trying to build a trajectory model that considers air-friction. The first step, I reckon is to find the Function of both vertical and horizontal displacement with time, then I can use ...
1
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1answer
136 views

How to simulate Multifractional Brownian Motion?

The maximum I would ask, is hints, how to model MFBMotion. Link to paper Firstly, i wanted to simulate in MATLAB that code: ...
1
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0answers
47 views

Can I model the general political landscape with mathematica? [closed]

I want to develop a website which would model a province of 2 million people from a political point of view. Is mathematica a good fit for such a project? My background is that I'm an experienced ...
4
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1answer
192 views

Problem exporting and re-importing STL file

I wrote all code and there're no errors in code. Result of code is like first picture(left). But I can't Import that structure. The result of import stl file is second one(right one). How can I import ...
1
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1answer
107 views

Transposition of state space form of a transfer function

How can I transpose the output of state space model in Mathematica? trying the following code would transpose the top right symbol s instead of the matrices. ...
2
votes
1answer
94 views

Extract Transfer Matrix from TransferFunctionModel

I have a MIMO transfer function model, and I'd like to know how to perform arithmetic on this model. For instance, to see the difference between two systems' outputs for arbitrary inputs, I'd like to ...
1
vote
0answers
245 views

Solution to heat equation with Neumann boundary conditions and lateral heat loss

I am conducting an experiment on heat conduction in a copper rod. To do so I am using a thin copper rod with several temperature probes, then I am going to compare the data with a solution to the heat ...
1
vote
1answer
203 views

Modeling a stellar atmosphere

I'm trying to model a stellar atmosphere using Mathematica. Basically I'm working in a physical and chemical model which combined should give me a profile of the chemical abundance in the atmosphere. ...
1
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1answer
160 views

Animating a 3D shape along path a (2D and 3D) parametric function curve [Update]

I have a 3D object under the action of gravity field.The trajectory of path is a parabola.I would like to animate , as in the example GIF. ...
0
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2answers
119 views

Martingale pricing_Simulation random walk stock price

I need to make an example of a walk of a stock price.I have this data: and i need to resolve this equation: where "W" is a Wiener process [0,Δt]. I need to make a path of 157 steps(date of ...
7
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2answers
407 views

Find fit of an experimental PDF

After quite some struggle, I managed to put up a code that is syntaxically correct. The goal is to find the parameters for a gamma distribution that best match experimental data. The data is a set of ...
2
votes
1answer
126 views

How can I calculate the maximum number of grid layout possibilities?

I am doing some modelling where I am trying to randomly layout some points on a grid. What I know: How big the grid is The number of objects that have to be laid out on the grid, at a point The ...
1
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1answer
87 views

Multivariate Exponential Distribution in Mathematica

Is there a way to define a multivariate exponential distribution based on independent univariate exponential distributions (Akin to multinormal distribution): ...
1
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0answers
102 views

Disease Network Model Using NDSolve

I have a basic disease model using NDSolve: ...
7
votes
1answer
349 views

Computing launch parameters for hitting a point in 3D with projectile under influence of wind

The end goal of this problem is to compute functions which describe the launch parameters which are needed to hit a specified goal in 3D in the presence of wind disturbances. This is as far I have ...
1
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1answer
813 views

Fitting a Damped Sine to Data

I have some collected data that should be modeled by a damped oscillation. Here are the data in a list of ordered pairs: ...
3
votes
3answers
479 views

Plot Plane to Intersect 3D Contour Plot in Mathematica

I have a 3D model of a heart in Mathematica and I'm trying to create a plane so that the open surface (as seen in the image below) is cut off so that the heart can have a solid, level surface. How ...
6
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2answers
906 views

RSquared: LinearModelFit vs NonlinearModelFit

I'm trying to understand the differences between LinearModelFit and NonlinearModelFit. One thing I notice is that the ...
2
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0answers
192 views

How can I model the volatility, using a GARCH(1,1), of a time series of returns (and plot it) using Mathematica?

I know that if I use this code: tsm = TimeSeriesModelFit[ret, {"GARCH", {1, 1}}]; I can get the parameters using this: ...
0
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1answer
127 views

Fitting data with inclusion of constraints

How do I find a fit for the dataS (see below) with the constraint that the parameter np is an integer, and that the parameters la+lc = 100. A weak attempt at this is provided below for a specific ...
1
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0answers
51 views

Parameters in NDSolve for an Accurate Graphical Output — What to Tweak?

Friday Greetings, I'm working on an ODE system as a basic model for cancer treatment: $\begin{array}{c} \frac{{dN}}{{dt}} = kN\left( {1 - \frac{N}{\alpha }} \right) - \mu CN\\ \frac{{dC}}{{dt}} = ...
5
votes
2answers
131 views

ToDiscreteTimeModel fails following video

Following the systems-modeling video here at about 15 min, 20 seconds in, the presenter (Bob Sanhedrick, I think) shows a model for an "Asteroids-game"-like 2D spacecraft. The model is trivial: ...
3
votes
1answer
217 views

How to combine objects from different .obj files?

I got a screw .obj model with the head diameter of 2cm, and a board .obj model of 10cmx10cmx4cm in dimension. I would like the ...
2
votes
0answers
79 views

Determining the total illumination of a polygon

Is it possible to determine the total illumination of a particular polygon with the given light sources? I truly acknowledge that Mathematica is not supposed to do this modeling, but it is what ...
3
votes
1answer
232 views

Problem with SARIMA Time Series Model

I'm in the process of becoming familiar with some on the version 10 new functionality. I have two data sets, datasetA and datasetC, of time series data that I would like to make forecasts on. Here is ...
1
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1answer
184 views

Creating an animated graph model based on equations

So I have a graph that looks like this ...
2
votes
1answer
517 views

Model fitting to noisy data with a custom minimization function

I'm looking into fitting some data with Mathematica. I've got my head around how NonlinearModelFit works (I've been using the Levenberg-Marquardt algorithm for some ...
7
votes
0answers
613 views

Modelling Hysteresis with a Differential Equation

I want to implement the bulk ferromagnetic hysteresis model (mostly the Jiles-Atherton Model), see http://drum.lib.umd.edu/bitstream/1903/6043/1/PhD_99-1.pdf page 44 equation (30). The needed ...
0
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4answers
161 views

RSolve fails on a two-equation non-linear system

I have a system of just two recurrence equations, I need to solve them and so I use RSolve: ...
1
vote
1answer
171 views

In a manipulatable graph, display x values of all intersections with one of the lines?

I'm doing a project about Moore's law, I'm trying to create a graph that which you can manipulate, but I want the x-values of the intersections with one the lines to be displayed; how would I go about ...
4
votes
3answers
428 views

Approximate minimum degree permutation algorithm in Mathematica

In MATLAB there is a nice implementation of the so called AMD (approximate minimum degree permutation) algorithm named amd (see Online MATLAB Documentation). There is an alternative algorithm called ...
10
votes
1answer
1k views

How does Mma compute Confidence Intervals?

I am trying to understand how Mma computes the Confidence Intervals after a NonlinearModelFit. Consider the following example: ...
10
votes
1answer
499 views

Modelling the effect of a structure on a “tsunami” (hyperbolic wave equation)

So, the hyperbolic wave equation can be quite easily solved in Mathematica like this: ...
7
votes
1answer
840 views

Modelling a Rocket Launch using NDSolve

I'm trying to model a rocket launch with Mathematica but I've run into a little problem since I don't know how to turn the thrust off. I'm using Newton's Law of Universal Gravitation plus an added ...
0
votes
3answers
247 views

Given a Boolean representation of a system, how can the Reliability Function be displayed as symbolic algebra?

Can Mathematica 9 convert a Boolean representation of an RBD to its symbolic algebraic form? If I have a simple series Reliability Block Diagram made up of 2 components, c1 and c2 bexpr1=And[c1,c2] ...
3
votes
1answer
356 views

ParametricNDSolve and Constraint satisfaction problem

I am trying to find the values of two parameters that allow for a specific result of my differential equations, under different initial conditions. Given a system of equations: ...
1
vote
0answers
108 views

Can we ask ComponentMeasurements to use NonLinearModelFit to return a covariance matrix for underlying intensity data?

I'd like to be able to calculate a covariance matrix for some data underlying a morphological component. Provided this data, I can write something like: ...
0
votes
1answer
155 views

How to simulate a multivariate recursive system from a list

New to mathematica, trying to use Eric Swanson's Pertubation AIM program to solve DSGE models. His code produces a solution as a list or a table. My question is how do I use this list to simulate the ...
3
votes
1answer
670 views

Generating a “best fit” curve to a set of noisy data corresponding to a moving object

Please note that this is an extension of a previous question: Interpolating a sparse list of two-dimensional coordinates We have an ordered array of coordinates corresponding to the position of an ...
5
votes
1answer
661 views

Plot two functions within manipulate

I just want to plot all stochastic processes and their average process. The original code without the average is: ...
0
votes
1answer
120 views

Solving one equation, then inputting the values into another for NonlinearModelFit

Considering the equation a*x^3 + a*x^2 + x + b == 0 I'm looking to find the best value for a and ...