Questions tagged [modeling]
Questions about approaches for simulating physical systems or phenomena by building from related understanding and basic principles.
194
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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. ...
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1
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485
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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.
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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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2
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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 ...
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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 ...
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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 ...
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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:
...
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4
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3
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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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RSquared: LinearModelFit vs NonlinearModelFit
I'm trying to understand the differences between LinearModelFit and NonlinearModelFit. One thing I notice is that the ...
- 411
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460
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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:
...
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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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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}} = ...
- 11
6
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2
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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 ...
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358
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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 ...
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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 ...
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637
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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 ...
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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 ...
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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 ...
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4
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253
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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:
...
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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
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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 ...
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315
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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]
...
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3
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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
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143
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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:
...
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266
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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 ...
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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 ...
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809
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Plot two functions within manipulate
I just want to plot all stochastic processes and their average process.
The original code without the average is:
...
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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 ...
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5
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4
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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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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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542
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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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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 ...
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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/...
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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-...
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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 ...
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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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How to do System Dynamics simulations / diagrams in Mathematica?
System Dynamics is an approach to understanding the behaviour of complex systems over time. It deals with internal feedback loops and time delays that affect the behaviour of the entire system. What ...
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