Questions tagged [non-linear]
60 questions
4
votes
1 answer
Generating sequence of numbers in Python (curved)
I am trying to generate, say a non-linear sequence of 120 numbers in a range between 7 and 20.
I have already tried using numpy geomspace and logspace, which gave me pretty much the same outcome. It does what I want, but the resulted "curve" is not…
EvolveX
- 43
- 3
3
votes
0 answers
Efficiently use Eigen for repeated sparse matrix assembly in nonlinear finite element code
I am trying to use Eigen to efficiently assemble a Stiffness matrix for non-linear finite element computations.
From my finite element discretization I can exactly extract my sparsity pattern. Therefore I can just…
rath3t
- 101
- 4
3
votes
1 answer
How to build process simulator in gekko knowing time constant and steady-state values
I have a very complicated non-linear dynamical system for which I know time constant and steady-state responses at each time instance from CFD (Computational Fluid Dynamics). How do I (1) build a process simulator using this information? and (2) how…
Shailendra Kaushik
- 31
- 2
2
votes
2 answers
Can a neural network having non-linear activation function (say ReLU) be used for linear classification task?
I think the answer would be yes, but I'm unable to reason out a good explanation on this.
vasu
- 173
- 1
- 11
2
votes
1 answer
Find average value of variable in an interval in MATLAB
I have some data inside MATLAB. On the picture you can see a small portion:-
The numbers I'm interested in are RPM and Lambda. As you can see, they are neither strictly decreasing or increasing (they are non-linear so to speak). I want to find the…
Carl
- 149
- 1
- 7
2
votes
2 answers
Mode 9 is infeasible GEKKO
I successfully performed this simulation in mode 6, this is a microalgae model. I want to compare it with mode 9. But mode 9 is always infeasible. Any suggestion?
About how can I fix mode 9?
I try we different initial conditions but ti doest not…
ldsangr3
- 35
- 4
2
votes
1 answer
How to use integration in Nonlinear Data-Fitting: Fsumsquares and then fminunc for parameter optimization
I am able to run the code for any equations but when I introduce an integral the command won't run:
t=dataset_TK1(:,1);
dataset_TK4=xlsread('Akis','Sheet1','AG491:AR725');
y_4=dataset_TK4(:,12);
Kg=1.76717865712934;
N0=1.08E+05;
fun1=@(Z)…
Akis Kesisoglou
- 21
- 1
2
votes
1 answer
Issue with Mixed Integer Non-Linear Programming problem in GEKKO
I am using GEKKO for solving an MINLP problem in Python that involves a co-simulation with PowerFactory, a power system simulation software. The MINLP problem objective function needs to call PowerFactory from within and execute particular tasks…
Soudipan Maity
- 31
- 3
1
vote
0 answers
Simulating non-linear ARX model doesn't work
I estimated a non-linear ARX model with the sytem identification toolbox in matlab and tried to simulate the response to a validation data set. Unfortunatly the response seems to be not stable and doesn't lead to the results obtained from the…
Fibaro
- 11
- 2
1
vote
0 answers
nonlinear Schroedinger equation resolution with split step method
I'm trying to resolve a nonlinear PDE Schrödinger equation with the split-step Fourier pseudo-spectral method. The fonction "solver" is supposed to solve the time and space dependant equation with the split-step method but it gives values…
rbalint99
- 11
- 1
1
vote
1 answer
OR-Tools (CP-SAT) - How to implement a non-linear function
I'm attempting to use Google's OR-Tools to produce a distance constraint between 2x 2D points (p0 & p1).
This becomes the non-linear expression:
(p1x - p0x)² + (p1y - p0y)² = d²
I have attempted to produce this with the CP-Sat solver using the…
Max Peglar-Willis
- 97
- 9
1
vote
1 answer
Why are some of my equations ignored when solving a non-linear system of equations
I am trying to solve a system of non-linear equations. The issue is that my input values are being returned to me as a valid solution. In order for this to happen, some equations have to be ignored. I have tried both sympy.solvers.nsolve() and…
Thomas Murdoch
- 13
- 2
1
vote
2 answers
How to calculate multi-variable nonlinear regression in python?
I am trying to create a program about non-linear regression. I have three parameters [R,G,B] and I want to obtain the temperature of any pixel on image with respect to my reference color code. For example:
Reference Files R,G,B,Temperature =…
Neo Aerospace
- 11
- 2
1
vote
1 answer
cellvariable*Diffusion in fipy
I am trying to solve the following coupled pde's in fipy. I tried the following
eq1 = (DiffusionTerm(coeff=1, var=f)-f*DiffusionTerm(coeff=1, var=phi)
+f-f**3 == 0)
eq2 = (2*DiffusionTerm(coeff=f, var=phi)+f*DiffusionTerm(coeff=1, var=phi)
…
Josiah Cochran
- 11
- 1
1
vote
1 answer
Fit of multiple nonlinear curves with Python
Let's say that we have a curve that have an n-number of curves that are contributing to its shape. In my basic example, working with NMR peaks, I have 3 peaks defined:
Here, I have used the following method for fitting these three peaks at…
