Questions tagged [modeling]

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

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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 vote
485 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. ...
• 13.1k
1 vote
481 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 ...
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1k 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 ...
• 167
337 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 ...
• 43
1 vote
158 views

Disease Network Model Using NDSolve

I have a basic disease model using NDSolve: ...
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689 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 ...
• 462
6k 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: ...
1k 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 ...
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4k views

RSquared: LinearModelFit vs NonlinearModelFit

I'm trying to understand the differences between LinearModelFit and NonlinearModelFit. One thing I notice is that the ...
• 411
460 views

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

I know that if I use this code: tsm = TimeSeriesModelFit[ret, {"GARCH", {1, 1}}]; I can get the parameters using this: ...
1 vote
1k 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 ...
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1 vote
73 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}} = ...
214 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 ...
• 8,641
358 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 ...
• 4,641
107 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 is ...
• 429
637 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 ...
• 1,377
1 vote
235 views

Creating an animated graph model based on equations

So I have a graph that looks like this ...
• 319
1k 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 ...
• 8,678
1k 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 ...
• 263
253 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
275 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 ...
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967 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 ...
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How does Mma compute Confidence Intervals?

I am trying to understand how Mma computes the Confidence Intervals after a NonlinearModelFit. Consider the following example: ...
• 2,118
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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: ...
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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 ...
• 1,557
315 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] ...
• 1,377
504 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: ...
• 2,118
1 vote
143 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: ...
• 11
266 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 ...
• 11
939 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 ...
• 1,123
809 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: ...
• 361
142 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 ...
1k views

Problem with WhenEvent

I am trying to add a time dependent fraction to a parameter in NDSolve, i.e. when 10 < t< 20, add ...
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883 views

How do I represent a system dynamics feedback loop?

In System Dynamics, if I want represent the relationship between Speed and Distances, I create a Flow (Speed) and a Stock (Distance) as you can see in this Insight Maker Sample . Heres an Image of how ...
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Mathematica Implementations of the Random Forest algorithm

Is anyone aware of Mathematica use/implementation of Random Forest algorithm?
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Sinusoid modelling

There are lots of great demonstrations that show how to get periodic functions in the unit circle. I'm wondering how hard it would be to simulate a "moving grid" similar to this video on youtube (...
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901 views

What's the analogue of UML in Mathematica land?

What's the analogue of Unified Modeling Language (UML) in Mathematica land? Mathematica has elements of object-orientation, but most Mathematica programs or applications aren't of object-oriented ...
• 8,594
3k views

Mathematica Package for Bayesian Networks

Are there any packages that allow the simulation of Bayesian Networks with Mathematica? I found what seemed to be a promising package (Dynamics) on a Brown University URL, http://www.cs.brown.edu/...
1k views

How to perturb a Dynamic System?

I'm trying to model a basic feedback system with delayed feedback. I've done the initial setup and now want to add a few more advanced features to my system. Currently, it's just a simple delayed-...
• 321
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How to model Macroeconomic dynamics?

I am rather new to Mathematica and I wanted to see if I could get some help with the following. I am trying to generate a model of macroeconomic indicators defined by the following functions, but I ...
756 views

PlotRange problems

I have a Delay Differential Equation of the form: ...
987 views

Sensitivity Analysis: Global Sensitivity and Screening

I have a model which accepts several input parameters and now I want to study the sensitivity to certain parameters as described in here: Cross Validated Answer and in Wikipedia. There is also a link ...
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