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1
vote
0answers
33 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
103 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
102 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
64 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
105 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
vote
1answer
138 views

Creating an animated graph model based on equations

So I have a graph that looks like this ...
2
votes
1answer
258 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 ...
0
votes
4answers
141 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: ...
0
votes
0answers
35 views

How does one use StandbyDistribution to model the reliability of an M of N warm standby system when M > 1?

I am modeling the reliability of a system with four units, numbered 1 through 4. The system needs at least two of the four units to be operational. Initially units 1 and 2 are active and units 3 and ...
0
votes
0answers
43 views

Write nth line to file [duplicate]

I have a code that I am running on a supercomputer. Currently the algorithm must finish before I can export any results from the algorithm. What I would like to do is to have the algorithm write out ...
0
votes
0answers
191 views

Non linear model fit mathematica

I want to fit experimental data (temp,alpha) to the following equation for calculating k and Ea -Log[alpha]^n = function(k,Ea,temp) However i do not know ...
2
votes
1answer
114 views

LinearModelFit of WeatherData

I am trying to perform a linear regression on some weather data, but I can't seem to figure out how to perform the operation. What I have right now is this: ...
1
vote
1answer
108 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 ...
0
votes
0answers
101 views

Making a predictive statistical model

I am totally new to Mathematica, and I have never used a similar program, apart from perhaps Excel (and I didn't even use Excel on a professional level). So I want to create a mathematical model ...
4
votes
3answers
256 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 ...
7
votes
1answer
400 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: ...
3
votes
1answer
241 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: ...
6
votes
1answer
511 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
200 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
200 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
94 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
120 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
409 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
462 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
91 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 ...
2
votes
4answers
316 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 ...
3
votes
2answers
322 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 ...
18
votes
5answers
2k views

Mathematica Implementations of the Random Forest algorithm

Is anyone aware of Mathematica use/implementation of Random Forest algorithm?
10
votes
3answers
359 views

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 ...
11
votes
2answers
421 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 ...
9
votes
2answers
912 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, ...
14
votes
3answers
538 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 ...
3
votes
2answers
478 views

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 ...
5
votes
0answers
233 views

Second-Order Feedback Pathways

I'm relatively new to Mathematica and I've tried searching and reading through the Mathematica documentation but I'm not able to find a good place to start. I want to model a simple, second-order ...
2
votes
1answer
403 views

PlotRange problems

I have a Delay Differential Equation of the form: ...
6
votes
0answers
400 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 ...
12
votes
3answers
2k views

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 ...