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How to get the exact step size used by ode45?
If the stepsize is part of the ODE equation, you cannot use ODE45 to solve. You have to write your own integrator.

29 days ago | 0

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Optimization Eigenvalue problem Stiffness matrix
Should be % Perform optimization [K_opt_vec,~,res] = lsqnonlin(@(K) obj_function_reshaped_matrix(K, M, f_exact_Hz), [k1_guess,...

1 month ago | 0

Answered
MATLAb Solve function not solving
Which MATLAB version are you using ? R2024b gives a direct answer: clear all close all syms I1 I2 V0 s=2; eqns=[5*I1+4*...

1 month ago | 1

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how can I calculate euler constant
g = vpa(eulergamma())

1 month ago | 1

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How to find the equation of a 2D plane that best fits a set of vectors defined in n dimensions?
https://stackoverflow.com/questions/48200261/fit-plane-to-n-dimensional-points-in-matlab

1 month ago | 1

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Answered
How to obtain direct symbolic solutions without introducing intermediate variables like z and z1 in MATLAB's solve function?
If it can't, I want to see what is the z and z1 in the solution. k,l,x,z and z1 are arbitrary numbers that satisfy joint_soluti...

1 month ago | 0

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Answered
How to Set a Minimum Step Size for Variables in GA Solver (Global Optimization Toolbox)?
Define 21 integer variables x_i that can take values 0 or 1 (by using the "intcon" input to "ga" and setting the lower and upper...

1 month ago | 0

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Trying to create a polynomial using data from a table
You can't expect exact agreement, but the approximation is not that bad (at least for the point chosen): % Data preparation dP...

1 month ago | 0

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Algebraic variable derivatives in the DAE solution process
0 = dg/dx * x' + dg/dy * y' + dg/du * u' = dg/dx * f + dg/dy * y' + dg/du * u' Solve for y'.

1 month ago | 0

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System of state dependent delay equations causes ddesd to run forever.
y(5) is negative shortly after t = 0. Thus your delay d = t - y(5) in principle would refer to values of y(1) that are not yet k...

1 month ago | 0

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Integrating multivariate Gaussian pdf in 4 dimensions
Use "mvncdf": https://uk.mathworks.com/help/stats/mvncdf.html If your function is more complicated than posted, try "integralN...

1 month ago | 0

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Answered
The mean function isn't working and i don't know why
Check whether the data type of Data_IV_KE is "double". To this end, MATLAB should return "double" when you type class(Data_IV...

1 month ago | 0

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Solving Second-Order BVP with unknown Constants using fsolve
solinit = bvpinit(linspace(-6.17415,6.17415,64),[0;0],[.809827,0]); sol = bvp4c(@mat4ode,@mat4bc, solinit); xint = linspace(...

1 month ago | 0

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Answered
Hi,I tray RUN this code but i get tis error ( below the code)
Variables and/or functions are missing to run your code. According to the error message, m90_plot is an array of size 12784, bu...

2 months ago | 0

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expressing the complex function
Use syms x t real instead of syms x t Then real(series) and imag(series) will work.

2 months ago | 0

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beginner integration trouble.
"int" cannot find an analytical antiderivative for f(x). Thus to get the numerical value for the integral, use Area=2*vpainte...

2 months ago | 0

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How to loop through values?
Beta = linspace(0,1,10); Alpha = linspace(0,2,20); n = numel(Beta); m = numel(Alpha); Result = zeros(n,m); for i = 1:n ...

2 months ago | 0

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Answered
Using erfcinv and array indices are being rejected as not positive or valid, despite all being positive in the vector
As far as I understand, "erfbatp" is an array of numbers. So erfbatp(2*.05/2) = erfbatp(0.05) does not make sense, does it ? V...

2 months ago | 0

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Converting symbolic ODE solution to function ... Warnings
The solution is implicitly given by the equation (a*y+b*y^2/2+c*y^3/3+d*y^4/4)-(a*y0+b*y0^2/2+c*y0^3/3+d*y0^4/4) - integral_{x'...

2 months ago | 0

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convert the above expression into this graph
I'll show you how to solve for theta2 given theta from the equation sin(theta2-theta)+exp(-theta2/(omega*tau))*sin(theta)=0 F...

2 months ago | 1

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Trouble using ODE45 for coupled non-linear differential equation
I can't recover the four differential equations you solve from the two equations you included in mathematical form. Your equati...

2 months ago | 0

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How to get the answer from the following code. How can i extract the values from the code?
F = U1.y(5,1)-Nt*U1.yp(5,1) J = -1i*U1.y(6,1) N1 = -U1.y(7,1) N2 = -U1.y(8,1)

2 months ago | 0

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Answered
Explicit method for Allen-Cahn equation
xstart = -1.0; xend = 1.0; nx = 401; x = linspace(xstart,xend,nx).'; dx = x(2)-x(1); tstart = 0.0; tend = 1.0; nt = 10; ...

2 months ago | 0

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Answered
How to fill a variable with the results of an if...elseif statement
Use imin = 0; imax = 0; isaddlePts = 0; iinconcl = 0; for ind = 1:9 D=fxx(Xc(ind),Yc(ind))*fyy(Xc(ind),Yc(ind)) - (fx...

2 months ago | 0

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Answered
Need to rectify error in my matlab code given below
I want to get a plot of dn/dt versus t. syms t mu=2500*(10^-4); %cm^2*V^-1 * s^-1 R = 0.318; eta=377;% ohm N=3.681; %refind...

2 months ago | 0

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Using Runge Kutta to solve second-order differential equations with two degrees of freedom
I don't understand from your code if you want to perform a parameter study for 1000 different values of omega or if you want to ...

2 months ago | 0

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Cannot get fmincon to work
clear close clc format long %% Variables dp = 11.6; taup = 3710e-6; dn = 2; taun = 371e-6; Jl = 50e-3; ni = 9.696e9; ...

2 months ago | 1

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Answered
I continue to get this error and can't figure out how to fix it, Unable to perform assignment because the size of the left side is 1-by-4 and the size of the right side is 1-b
If you take the derivative of a polynomial, the degree of the resulting polynomial is one less than the degree of the original p...

2 months ago | 0

Answered
coupled differntial equation using ode45
G = 1; Na = 1; xstart = -1; xend = 1; nx = 51; x = linspace(xstart,xend,nx); solinit = bvpinit(x, [0;0;1;0]); sol = bvp...

2 months ago | 1

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Answered
coupled differntial equation using ode45
syms y mu0 G Na U(y) T0(y) eqn1 = diff(mu0*diff(U,y)) == G; eqn2 = diff(T0,y,2) + Na*mu0*(diff(U,y))^2 == 0; conds1 = [U(-1)=...

2 months ago | 0