# Modeling and simulation **URL:** https://scilab.discourse.group/c/specific-domains/modeling-and-simulation/14.md [Latest](https://scilab.discourse.group/latest.md) · [Categories](https://scilab.discourse.group/categories.md) · [Tags](https://scilab.discourse.group/tags.md) --- ## [About the Modeling and simulation category](https://scilab.discourse.group/t/about-the-modeling-and-simulation-category/20)
**Author:** [@mottelet](https://scilab.discourse.group/u/mottelet)\ **Replies:** 0
Everything about differential equations, partial differential equations, … and computing their solutions. --- ## [Datafit error message: Hot restart: dimension of working table (argument n:-245447011)](https://scilab.discourse.group/t/datafit-error-message-hot-restart-dimension-of-working-table-argument-n-245447011/1053)
**Author:** [@Samuel.Enibe2](https://scilab.discourse.group/u/Samuel.Enibe2)\ **Replies:** 2\ **Last updated:** [October 6, 2025, 1:57pm UTC](https://scilab.discourse.group/t/datafit-error-message-hot-restart-dimension-of-working-table-argument-n-245447011/1053 "2025-10-06T13:57:44Z")
I have tried to use the datafit function to solve a non linear regression problem. It generates the error message “Hot restart: dimension of working table (argument n:-245447011).” I have changed the initial estimates b… --- ## [Nlinregr non linear regression function](https://scilab.discourse.group/t/nlinregr-non-linear-regression-function/1043)
**Author:** [@Samuel.Enibe2](https://scilab.discourse.group/u/Samuel.Enibe2)\ **Replies:** 4\ **Last updated:** [October 6, 2025, 7:01am UTC](https://scilab.discourse.group/t/nlinregr-non-linear-regression-function/1043 "2025-10-06T07:01:13Z")
nlinregr non linear regression function I created a SCILAB script and related functions to perform non linear regression of some data. I chose nlinregr because of the possibility of getting the regression coefficients. … --- ## [Polynomial roots, Davidenko method (1953) and the gamma trick](https://scilab.discourse.group/t/polynomial-roots-davidenko-method-1953-and-the-gamma-trick/950)
**Author:** [@mottelet](https://scilab.discourse.group/u/mottelet)\ **Replies:** 2\ **Last updated:** [May 23, 2025, 3:30pm UTC](https://scilab.discourse.group/t/polynomial-roots-davidenko-method-1953-and-the-gamma-trick/950 "2025-05-23T15:30:27Z")
How can you compute all the roots of an arbitrary polynomial if you are only allowed to use an ode solver ? Let us consider two polynomials p\_1 and p\_2 of degree n. A way of finding the the roots of p\_1 by homotopy from… --- ## [Expm versus ode](https://scilab.discourse.group/t/expm-versus-ode/802)
**Author:** [@Jens](https://scilab.discourse.group/u/Jens)\ **Replies:** 7\ **Last updated:** [February 3, 2025, 3:51pm UTC](https://scilab.discourse.group/t/expm-versus-ode/802 "2025-02-03T15:51:34Z")
Hello Scilab community, The following script is to solve the homogeneous ODE z'=Az with initial value z\_0. arkode does what I expect, expm does not. What has to be changed with the expm way? //ode\_vs\_expm.sce clear clc… --- ## [Evans function invalid index error](https://scilab.discourse.group/t/evans-function-invalid-index-error/773)
**Author:** [@anwerified](https://scilab.discourse.group/u/anwerified)\ **Replies:** 1\ **Last updated:** [January 6, 2025, 12:44pm UTC](https://scilab.discourse.group/t/evans-function-invalid-index-error/773 "2025-01-06T12:44:50Z")
s = poly(0, 's'); n1=(s+2); d1=(s+3)(s^2+2\*s+2); h1= syslin('c', n1,d1); disp(h1); evans(h1,50); there is no error, but the graphic window number 0 is blank. --- ## [Precision of arkode( ) vs. ode( ) at astronomical orbit simulation](https://scilab.discourse.group/t/precision-of-arkode-vs-ode-at-astronomical-orbit-simulation/674)
**Author:** [@Jens](https://scilab.discourse.group/u/Jens)\ **Replies:** 5\ **Last updated:** [October 23, 2024, 7:46am UTC](https://scilab.discourse.group/t/precision-of-arkode-vs-ode-at-astronomical-orbit-simulation/674 "2024-10-23T07:46:56Z")
If I use ode() to simulate the two-body problem sun-earth (state vector of 12 barycentric coordinates), there is a large discrepancy between the numerical and the analytical solution: In a simulation time of 550 (analyti… --- ## [Check progress of ode() execution](https://scilab.discourse.group/t/check-progress-of-ode-execution/643)
**Author:** [@Jens](https://scilab.discourse.group/u/Jens)\ **Replies:** 2\ **Last updated:** [September 16, 2024, 11:53am UTC](https://scilab.discourse.group/t/check-progress-of-ode-execution/643 "2024-09-16T11:53:26Z")
If the execution of ode() lasts for hours it would be helpful to get an intermediate information about how far ode has come, e. g. by periodic output of t. How can I modify the derivative function to this purpose? Given… --- ## [In search of more efficient computations](https://scilab.discourse.group/t/in-search-of-more-efficient-computations/615)
**Author:** [@heinznabielek](https://scilab.discourse.group/u/heinznabielek)\ **Replies:** 3\ **Last updated:** [August 31, 2024, 1:18pm UTC](https://scilab.discourse.group/t/in-search-of-more-efficient-computations/615 "2024-08-31T13:18:05Z")
Colleagues, I have already solved my problem and a much simplified example is shown below. I am asking are there ways for more efficient computations of ‘Model(time)’ when it comes to huge arrays and much more complex m… --- ## [ATOMS CPGE Toolbox](https://scilab.discourse.group/t/atoms-cpge-toolbox/466)
**Author:** [@JBosselmann](https://scilab.discourse.group/u/JBosselmann)\ **Replies:** 4\ **Last updated:** [April 24, 2024, 9:41am UTC](https://scilab.discourse.group/t/atoms-cpge-toolbox/466 "2024-04-24T09:41:14Z")
Hi, I have installed SciLab 2023 recently and I would like to generate Bode-Plots with Xcos. Does the Toolbox CPGE work with this SciLab Version? Thanks a lot for your helb. Best regards --- ## [Seeking Insights on Modeling a Nonlinear Dynamic System in Xcos\*](https://scilab.discourse.group/t/seeking-insights-on-modeling-a-nonlinear-dynamic-system-in-xcos/443)
**Author:** [@Smart](https://scilab.discourse.group/u/Smart)\ **Replies:** 5\ **Last updated:** [March 28, 2024, 1:46pm UTC](https://scilab.discourse.group/t/seeking-insights-on-modeling-a-nonlinear-dynamic-system-in-xcos/443 "2024-03-28T13:46:30Z")
I am working on a project that involves modeling a specific nonlinear dynamic system in Xcos. The core of the system is defined by the step response function: y(t) = y(0) + \\frac{Po}{f} \\cdot A \\cdot (1-\\exp(-\\frac{t}{… --- ## [Model a first order system with input delay - Padé approximant?](https://scilab.discourse.group/t/model-a-first-order-system-with-input-delay-pade-approximant/388)
**Author:** [@scelles](https://scilab.discourse.group/u/scelles)\ **Replies:** 8\ **Last updated:** [March 6, 2024, 9:40am UTC](https://scilab.discourse.group/t/model-a-first-order-system-with-input-delay-pade-approximant/388 "2024-03-06T09:40:27Z")
Hello, I would like to model a 1st order system with delay in Scilab (not XCos). It was previously (in old versions of Scilab) possible to do s = poly(0, 's'); H = syslin('c', 1\*exp(-1.5\*s) / (1+4\*s)) time = linspace(… --- ## [Using kinsol to solve a nonlinear pde](https://scilab.discourse.group/t/using-kinsol-to-solve-a-nonlinear-pde/304)
**Author:** [@mottelet](https://scilab.discourse.group/u/mottelet)\ **Replies:** 1\ **Last updated:** [December 21, 2023, 11:21am UTC](https://scilab.discourse.group/t/using-kinsol-to-solve-a-nonlinear-pde/304 "2023-12-21T11:21:07Z")
Hello, As you may have noticed, Scilab 2024.0.0 includes new nonlinear and differential/algebraic equation solvers using the SUNDIALS library (see SUNDIALS | Computing). A common feature of these solvers is the ability … --- ## [Xcos CLOCK\_c Period Setting](https://scilab.discourse.group/t/xcos-clock-c-period-setting/277)
**Author:** [@Smart](https://scilab.discourse.group/u/Smart)\ **Replies:** 10\ **Last updated:** [December 1, 2023, 8:16am UTC](https://scilab.discourse.group/t/xcos-clock-c-period-setting/277 "2023-12-01T08:16:33Z")
Hello, Enclosed, please find a screenshot along with the xcos model. I am seeking clarification on why the scope output varies with changes in the period time of CLOCK\_c. I’m unsure where my approach might be incorrec… --- ## [Adding initial conditions in a transfer function/block](https://scilab.discourse.group/t/adding-initial-conditions-in-a-transfer-function-block/209)
**Author:** [@ADG1977USER](https://scilab.discourse.group/u/ADG1977USER)\ **Replies:** 1\ **Last updated:** [October 25, 2023, 1:18pm UTC](https://scilab.discourse.group/t/adding-initial-conditions-in-a-transfer-function-block/209 "2023-10-25T13:18:29Z")
Good afternoon, everyone I have a question, and hopefully someone can assist me with it Is it possible to specify initial conditions for a transfer function in the XCOS ? I have a model with a numerator of 1 and a deno… --- ## [Retrieve ODE rhs values at solution in addition to solution values](https://scilab.discourse.group/t/retrieve-ode-rhs-values-at-solution-in-addition-to-solution-values/144)
**Author:** [@mottelet](https://scilab.discourse.group/u/mottelet)\ **Replies:** 4\ **Last updated:** [August 29, 2023, 11:33am UTC](https://scilab.discourse.group/t/retrieve-ode-rhs-values-at-solution-in-addition-to-solution-values/144 "2023-08-29T11:33:52Z")
I have recently answered this question on Stack Overflow and I think it would be valuable to share it. When the derivative (with respect to time) of the solution of an ode is expected, the usual way is to call the right …