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Stephan


856 total contributions since 2017

Knowledge means knowing where it is written...

Interested in:
- Optimization
- Mathematical Modelling
- Improvement of my programming skills

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Answered
linsolve time-consuming
Get rid of symbolic calculation - this makes code very slow and solve numeric: clear X Y % This works if your values are of si...

1 day ago | 2

Answered
Not able to solve an ode using dsolve
Consider: syms y(t) ode = diff(y,t) == -0.127.*(-3.*(log(7e-10.*exp(0.405.*y))).*(y - 0.01)); cond1 = y(0) == 0.01; co...

2 days ago | 0

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Answered
How to solve a system of third order non-linear differential equations
% create a 1.order system and a function handle syms u(t) w(t) r h nue eq(1) = diff(u,t,2) == -1/r*diff(u,t)+u/r-(1-nue)/2*r...

2 days ago | 0

Answered
logical expression in objective function
Hi, use the inequality constraints A and b as input arguments for the solver.

3 days ago | 0

Answered
Plotting a concatenated function (GUI)
https://de.mathworks.com/help/matlab/ref/str2func.html x=-5:.5:5 funy2=str2func('1.*x.^2+5*x+6') plot(x,funy2(x))

4 days ago | 1

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Answered
Why do I get 'Undefined function or variable'?
If u is calculated inside the function it should not be an input argument of the function. Also delete varargin - no need - resu...

6 days ago | 0

Answered
Fval Output by ga does not match output of fitness function evaluated at the respective x vector
you problably are are victim of rounding errors. try: FullDevice(x) to use the exact results of x as input for your Fitn...

11 days ago | 0

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Answered
Plotting the different solution via fzero solver against a range of one of the variable
N = 100; % define the parameters Nd = 1e23; e = 12*1e-12; %r = 0 R = 20*1e-9; Et_Ef = -0.21*1.6*1e-19; K = 1.3807e-...

18 days ago | 0

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Answered
Optimizing a matrix with cplexlp?
Hi, you could think about using graphs for this job: % your matrix A = [0 1 0 0 0 0 0 0 0 0; 1 0 1 0 0 0 0 0 0 0; 0...

19 days ago | 1

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Answered
lsqcurvefit cannot evaluate initial function, says insufficient input arguments
Have a read here: https://de.mathworks.com/matlabcentral/answers/465406-fmincon-error-not-enough-input-arguments it appears to...

20 days ago | 1

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Answered
Fmincon error not enough input arguments
Your objective function takes 2 input arguments - by default the optimization solvers only use 1 argument, which is the vector o...

21 days ago | 3

Answered
Why doesn't this code rotate and transform the spiral?
No for loop is needed: t = linspace( 0,4*pi,1000); r=@(t) sqrt(t); x = r(t).*cos(t); y = r(t).*sin(t); plot(x,y) %turns x...

21 days ago | 0

Answered
Solving two differential equations using ode45
This will help: https://de.mathworks.com/help/symbolic/odetovectorfield.html Follow the given examples and adapt them to your ...

21 days ago | 1

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Answered
can anyone help me ?
clear all; clc; close all; N=[100,200,300,400]; hold on for k=1:numel(N) %%les données mathématiques t = 0:1/(N(k)...

22 days ago | 0

Answered
Need to solve this
I assume you want real Solutions. Then try: syms a b c assume ([a b c], 'real') eq = [a+b == 204;... a+b*exp(-105*c) ==...

24 days ago | 1

Answered
How can I delete the elements of array on MATLAB?
To delete an array use: array1 = [];

25 days ago | 1

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Answered
ode23 and ode45 problem
% Solve symbolic (blue line in plot) syms y(x) x eqn = diff(y,x) == -2*x+4*y^2 sol_symbolic = dsolve(eqn,y(0)==0); fplot(sol...

29 days ago | 0

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Answered
substitute one cell of 3D matrix with another cell
A(:,:,158) = I; % where I is the 512x512 image you want to insert

29 days ago | 0

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Answered
How writing code sum 1+2+3+4+...+n
n = 4; A = sum(1:n)

1 month ago | 0

Answered
error variable y in fitness function
function y=fungsi3(x) y=2+exp(-(x(1).^2+x(2).^2)).*(sin(4*x(1))+cos(8*x(2))); end

1 month ago | 0

Answered
How can I expand x axis to have normal plot?
A(:,1)=data{:,1}; A(:,2)=data{:,2}; A=sortrows(A,1); plot(A(:,1),A(:,2))

1 month ago | 0

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Answered
Check to find if a row has an element occuring more than once
A = [0 0 1 1 0 0; 0 0 0 0 0 1; 1 1 0 0 0 1] res = (sum(A==1,2)>1) This works row-wise for more than 1 rows

1 month ago | 0

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Answered
how can I create a multiplication table and write it to spreadsheet in Matlab?
a = 1:5; t = a .* a' writematrix(t,'multiplication.xlsx')

1 month ago | 0

Answered
How do you give data as argument of fmincon?
<https://de.mathworks.com/help/optim/ug/passing-extra-parameters.html>

1 month ago | 1

Answered
ode45 with two 2nd order differential equation
<https://de.mathworks.com/help/symbolic/odetovectorfield.html>

1 month ago | 1

Answered
Solve a system of odes where equations are derived from a separate code (not directly given) using syms function
Hi, have a read here: <https://de.mathworks.com/help/symbolic/odetovectorfield.html> Best regards Stephan

2 months ago | 0

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Answered
Cannot use fzero function
i recommend to use fminunc: x=fminunc(@funct,pi/2); function y = funct(x) y=7.*sin(2.*pi.*x).^2 end

2 months ago | 1

Answered
Solving system of 3 nonlinear Equations
syms EPS0 E1 A1 E2 A2 RO e_y1 e_y2 e_z1 e_z2 I_y1z1 I_y2z2 M I_z1 I_z2 alfa fun1 = EPS0*(E1*A1 + E2*A2) - (1/RO)*(E1*A1*e_y1...

2 months ago | 0

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Answered
Creating transfer function (using tf) with unknowns in it
You might want to work with tuneable models / tuneable parameters.

2 months ago | 0

Answered
Find the intersection point between 2 curves
create a function handle depending from wave length, that subtracts both from each other. this is the objective function for usi...

2 months ago | 1

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