Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [matlab]

Questions about the numerical programming language MATLAB.

2
votes
1answer
59 views

Generate high n quantum harmonic oscillator states numerically

How can I generate the higher $n$ quantum harmonic oscillator wavefunction (in position space) numerically? Here, higher means around $n=500$, or say $n=2000$, where $n$ is the $n$th oscillator ...
-1
votes
0answers
31 views

System of coupled differential equations

I have a system of non linear coupled differential equations. I would like to use the finite difference to solve t but some left BCs are missing (though I have enough BCs to make it well posed). Can I ...
11
votes
3answers
1k views

Least squares approximation question

I am taking a course on scientific computation, and we just went over least squares approximation. My question is specifically about approximating using polynomials. I understand that if you have n+1 ...
0
votes
1answer
52 views

coupled equations with finite difference method

I have these three differential equations in which I need to solve numerically: $$ \frac{dn_0}{dt}= -n_0(t)W_{01}(t) + n_1(t)K_{10} $$ $$ \frac{dn_1}{dt}= -n_1(t)W_{12}(t) - n_1(t)K_{10} + n_2(t)K_{...
1
vote
1answer
81 views

Use Slepc from Matlab

Is there a direct way to use SLEPC from Matlab? I remember that in some old manuals there was some Matlab interface. However, in the last one, I cannot find any reference to this. For me it would be ...
5
votes
1answer
138 views

Matlab help related with the scaled Newton's iteration method

I need a little help with Matlab code for the method mentioned in this paper for computing the inverse of the matrix. In this paper, the author presented scaled Newton iteration given by $X_{k+1} = \...
-1
votes
0answers
60 views

Understanding how to solve DAE

I am solving the following pde that is discretized in space using method of lines, in MATLAB using ode15s. $$\frac{\partial C}{\partial t} = D\frac{\partial ^2 C}{\partial x^2}-v\frac{\partial C}{\...
1
vote
1answer
169 views

Efficiently generate a random subgraph (Gs) with maximum degree K, using only edges from an existing graph G

I am looking find a way of efficiently generating a random, undirected subgraph $G_s$ with $N$ vertices, using a subset of edges from an exisiting undirected graph $G$, also of size $N$, where the ...
0
votes
1answer
97 views

temperature profile on axial direction of a chamber

I have a task to plot average temperature profile at each cross-section in the axial direction of a combustion chamber. I have $x$, $y$, $z$ coordinates data in excel as well as the corresponding ...
2
votes
1answer
88 views

Analytical Solution of Transport Equation

I'm looking at the analytical solution of the convection-diffusion equation $$\frac{\partial C}{\partial t} = D\frac{\partial ^2 C}{\partial x^2}-v\frac{\partial C}{\partial x}$$ with initial ...
0
votes
1answer
95 views

Prescribing variables as an excitation in Runge-Kutta method

I am using Runge-Kutta to solve a $3 \times 3$ 2nd order linear ODE $$M x'' + C x' + K x = 0$$ and initial conditions are all zeros. Then I prescribe the 2nd variable to follow a given path. As for ...
1
vote
1answer
2k views

2D cross section from 3D surface

I am trying to apply the "restoring force surface" method to a dynamic linear system. The idea behind this method is that, knowing acceleration, displacement, velocity and input force it is possible ...
5
votes
1answer
9k views

How do I plot a transparent cylinder in matlab? [closed]

I know that I can use the following commands to create an opaque cylinder in matlab: N=100; [X,Y,Z]=cylinder(R,N); surf(X,Y,Z); I want to plot an arrow inside ...
1
vote
1answer
35 views

Wrong results for $2$ stage multistep method $y_{n+2} - y_n = h\left[(1/3)f_{n+2} + (4/3)f_{n+1} + (1/3)f_n\right]$

I need to fix a code to utilise the $2$ stage multistep method : $$y_{n+2} - y_n = h\left[(1/3)f_{n+2} + (4/3)f_{n+1} + (1/3)f_n\right]$$ Since this is an implicit method, I used a Newton-Raphson ...
-1
votes
0answers
33 views

Numerically solving 2D “time-dependent Schrödinger equation” in MATLAB

I need to numerically solve the following second-order ODE in MATLAB $$ 2ik\frac{\partial U(\vec{\rho},z)}{\partial z}+\left[\frac{\partial^2}{\partial x^2}+\frac{\partial^2}{\partial y^2}\right]U(\...
2
votes
0answers
46 views

How to find two points within defined region in this constrained optimization problem?

I am doing a project related to robotics where I am using fmincon function from matlab to minimize the distance between the points ...
9
votes
2answers
159 views

Numerical stability of higher order Zernike polynomials

I'm trying to calculate higher order (e.g., m=0, n=46) Zernike moments for some image. However, I'm running into a problem ...
0
votes
1answer
330 views

Finite Element Analysis for Laminated Plates with Holes or Patches

As the title says, I am trying to code in FEM a plate structure that either has a hole in one of the layers or one of the layers is made of patches of plates, rather than one whole plate. However, ...
6
votes
3answers
200 views

Nonlinear eigenvalue problem - MATLAB code

I'm trying to solve a nonlinear eigenvalue problem in MATLAB, still without success. It's a problem about graphene plasmonics. The nonlinear eigenvalue problem is given below: \begin{equation} \frac{...
1
vote
1answer
263 views

Pool two computers for MATLAB parfor without MDCS

I have two identical computers, both with 4 dual cores and MATLAB installed on them. They are connected to the same network. Is there anyway I can run a parforloop using the computation power of both ...
2
votes
1answer
182 views

Step-size selection for an Trapezoidal Method ODE solver (ode23t)

I was reading the documentation of the MatLab ODE solver ode23t, and I've seen that the trapezoidal rule is used. Moreover, the error is estimated by ...
8
votes
0answers
130 views

Tucker factorisation to compare multiple PCA decompositions?

This is an entry-level question for multiway matrix decompositions. I have a set/population $k$ of entities (here biological cells) for each of which I also have a number ($l$) of flavours of length $...
1
vote
0answers
81 views

Finite differences for the one-phase Stefan problem

I am trying to code the one-phase, one-dimensional Stefan problem using finite differences in Matlab, similarly to what has already been done in Mathematica (see https://mathematica.stackexchange.com/...
3
votes
2answers
216 views

Given x,y,z data of a periodic object, calculate the period of the object (if possible)

So the problem I am working on is as such. Given the x,y,z data of a periodic object over time (from the origin in 3d space) (need not be uniform), calculate the period of the object (if the data ...
6
votes
2answers
2k views

How can I generate half-normal variates in MATLAB?

I can find the random('normal', 0, 1, 10000,1) command in MATLAB but it generates half-normal variates. I would like to generate random half-normal variates. The ...
1
vote
1answer
93 views

Matlab parpool on Intel Xeon-Phi (KNL)

I am trying to run my matlab script on a Xeon Phi node with 68 physical cores. Using parpool I allocate 16 cores to enable SMD parallelization with a parfor loop. The script looks something like this. ...
4
votes
1answer
57 views

How to preserve or recover states meanings in canonical state-space realizations

Let assume that one would like to translate an input-output model, into a state-space one. It is well-known that the process of realization addresses this aspect. Let assume to have the following ...
2
votes
1answer
4k views

Nonlinear ODE to solve Duffing's equation

I am trying to solve the Duffing's equation in MATLAB. $ m\ddot{y}+c\dot{y}+ky+k_{3}y^{3} = f(t) $ where $ f(t) = A \sin{\omega t}$ To do that I wrote a function to be given to the ode45. ...
0
votes
2answers
57 views

Plot a multi-variable equation in (discontinuous) regions

The goal is to display the relation between K and E in the following equation: $$\cos(K) = 5 \text{sinc}( 5.12\sqrt{E} ) - \cos(5.12\sqrt{E} )$$ The intended result is: However, using the following ...
3
votes
1answer
1k views

How to compute the Helmholtz decomposition of 2D and 3D vector fields?

I have a sample of 100 particles with their 3D positions and velocities. I want to decompose the velocity vector field to its curl free and divergence free components. Is it a feasible to do so for ...
0
votes
1answer
32 views

How do I find the default ODE solver tolerances in Matlab?

You can set the Absolute or Relative ODE solver tolerances in Matlab with the options structure from an odeset command. But how do I find the default values for the ...
3
votes
0answers
2k views

Numerical integration and filtering of acceleration experimental data

I have a vector containing acceleration measurements and the corresponding vector of times in which measurements are taken. To obtain velocity and displacement I used the cumtrapz() function already ...
2
votes
1answer
30 views

Log-transformation of decision variables in parameter estimation

I am trying to find the diffusion coefficient ($D$) and the partition coefficient ($KLP$) using experimental data of desorption of a pollutant from a film into a liquid. This process can be modelled, ...
3
votes
1answer
230 views

How does fmincon in MATLAB calculate gradients?

I am trying to solve numerically a constrained optimisation problem in MATLAB, and I am wondering how the fmincon function calculates gradients when one isn't ...
12
votes
2answers
3k views

Why does Matlab's integral outperform integrate.quad in Scipy?

I am experiencing some frustration over the way matlab handles numerical integration vs. Scipy. I observe the following differences in my test code below: Matlab's version runs on average 24 times ...
0
votes
0answers
193 views

Need an explanation of setting Boundary Condition in pdepe (PDE Solver)

I am trying to solve the Advection-Diffusion equation using pdepe (PDE solver) in Matlab. I am not clear why we are writing ...
0
votes
1answer
788 views

MATLAB: code for restarted gmres

I have a question about Matlab and restarted gmres. I would like to use gmres.m provided here. This code seems to be popular for the scientific computation newcomer....
2
votes
0answers
101 views

Accelerate computation speed by using a different syntax [closed]

I was reading a book about Matlab ("Accelerating Matlab with GPU computing - A Primer with Examples" by Jung Suh and Youngming Kim, 2013. Chapter 1.7 Examples). I read an example where it said that: ...
0
votes
1answer
69 views

How to simulate thermal expansion in a 2D plane using FEA?

I am trying to model 2D thermal expansion of a square area inside another square using FEATool. I have simulated plane strain by incorporating forces pointing along the $[1 \,\,\, -1]^T$ direction ...
-1
votes
1answer
356 views

How to initiate spirals in this model?

I am trying to reproduce Tang & Othmer paper which is related to excitations and oscillations in G-protein model in Dictyostelium discoideum, an amoeba species. The mathematical model in the paper ...
6
votes
2answers
320 views

Matrix multiplication accuracy Matlab vs Python

I am translating some Matlab code into Python and I having some problems regarding matrix multiplication accuracy. Assuming we have following data: ...
1
vote
3answers
296 views

2D simulation of a particle with different diffusion coefficient in different directions of the particle

How can one simulate diffusion of a particle which has a natural axis and diffusion coefficient of the particle in the direction of the axis is D_1 and in perpendicular to the axis is D_2? Could ...
0
votes
1answer
116 views

maltab ode solver- user defined criteria to stop calculations

is there a way to add a user defined convergence criteria to an ode solver so that the solution is stopped? I know that Matlab uses absolute and relative tolerances but would that suffice in solving ...
7
votes
5answers
3k views

Minimizing $\mathrm{trace}(S)+\mathrm{trace}(S^{-2})$ using CVX

In Matlab, I would like to minimize the function $$f(S)=\mathrm{trace}(S)+\mathrm{trace}(S^{-2})$$ where $S \in \mathcal{M}_{m,m}$ is symmetric and positive definite, which is definitely a convex ...
0
votes
0answers
61 views

Applying base excitation to a MATLAB state-space

I have a state space model that was provided to me by exporting it from an external FEA program. The model can be described as $\dot x = Ax + Bu$ $y = Cx + Du$ This model assumes forces and ...
0
votes
0answers
51 views

How do I “push” matlab's lsqr solver to a particular solution?

The background to my problem can be found here: Iteratively solving a sparse, ill-conditioned system I have a function that now works well. When I give it test data, I recover the expected result. ...
0
votes
0answers
58 views

Methods for Parameter Scaling in Gradient-based Optimization

I am trying to minimize an objective function with 4 parameters, e.g., $a,b,c,d$ using gradient descent. $a < 0.1$, while $0 <b,c,d < 10$. I'm using a learning rate for all parameters on the ...
3
votes
0answers
96 views

Iteratively solving a sparse, ill-conditioned system

I have a sparse (density = 0.2%), ill-conditioned system that I am trying to solve, with no luck. Background I have a sequence of sampled data, where two of every 8 samples have been zeroed due to a ...