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how to ues the exponentials and derivatives in bvp4c
yp1 = deval(S,1) ym1 = deval(S,-1); T1= exp(-b1*(1+m))*ym1(4); T2= exp(-b1)*yp1(4); N1= -(1+b2*(1+m))*ym1(5); N2= -(1+b2)*y...

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Nonlinear time dependent 2D system of PDE's
I doubt there is a software capable to handle this kind of PDE system automatically. You will have to discretize the spatial d...

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How could I have these two erros when I did everything right (otherwise)?
c_p defined in your script does not mean that it is also visible in your functions. Either define the functions as nested funct...

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Problem with solving two differential equations depending on each other
Since W0 = 0, you get Re = 0 and thus lambda = something undefined (you divide by Re !). What does the c stand for in dm^3/c fo...

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How to plot function with different first x values?
I = @(R)0.5*(R>=0 & R<10)+5/R*(R>=10 & R<=100); U = @(R)0.5*R*(R>=0 & R<10)+5*(R>=10 & R<=100); P = @(R)I(R)*U(R); R = 0:0.1:...

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Why eigen vector looks different than the calculated one
Eigenvectors are only unique up to a multiplicative constant, and MATLAB's eigenvectors are normalized to be of norm 1: [1;-3]/...

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Paramter optimization using fmincon
It seems that the model is not able to reproduce your measurement data. The curves look qualitatively different. clc; clear; ...

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i make a code of shooting method for 3rd order differential equation but i dont get the accurate result
y20 = 2; sol = fsolve(@fun_shooting,y20); [X,Y] = fun_ode(sol); plot(X,Y(:,1)) function res = fun_shooting(y2) [X,Y] = ...

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Non linear system by Newton-Raphson
x1 = 1; y1 = 1; P = [x1 ; y1]; F= @(x,y) [atan(y)-y.*x.^2 ; x.^2+y.^2-2*x]; JF = @(x,y) [-2.*x.*y (1/(1+y.^2))-(x.^(-2)) ;...

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need help getting this to run
Maybe initial_strain_index = find(colum1 == min(colum1),'first'); peak_stress_index = find(colum3 == max(colum3),'first'); in...

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How to visualise the 'output' of a Neumann boundary condition?
I think the example "Heat Transfer Problem on a Square" under https://uk.mathworks.com/help/pde/ug/pde.stationaryresults.eval...

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Can PDE solver pdepe handle discontinous initial conditions?
Depends on the equation(s) you want to solve. If there is much diffusion in your equation(s), usually yes. Else usually no.

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one of the terms "Rho_net" on the RHS of an set is varying with time over the tspan. How do I implement the set of the ODEs such that the term updates at every time step?
If you insert the line size(dYdt(tspans(1),initial_conditions)) before the call to ode45, you will see that your function dYdt...

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Newton Raphson gives answers divided by 0
Your linear systems in the course of the Newton iterations cannot be solved since the Jacobian is rank-deficient (it has only ra...

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I am wanting to delete these entries of vector x when x = 0. How do I do this. Matlab gives me an error right now saying index cannot exceed 38 but I don't know what's wrong.
Use x(x==0) = []; instead of for i = 1:56 if x(i) == 0 x(i) = [] end end The length of the x-vector wil...

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I am trying to create a while loop where a marker can't leave a box of x = -10 and y = 10, y = -10. Once the marker reaches x = 11 I want the loop to stop.
Put the k = k+1 at the end of the while-loop, not at the beginning. And if x(k) == -10, you only set x(k+1), but not y(k+1). Th...

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solving for y in equation
a = 85.147; h = 55; v = 50; u = 25; f = @(x,y)x-sqrt(a^2+h^2)-(h-y).*cot(asin((h-y)/v))+(h-u)*cot(pi/4-asin((h-y)/v))+v*sin(...

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Iteration loop for a function to reach a certain value.
g=9.81; NU=2.52; k=.0293;%from book L=.025;%plate to cover spacing m sigma=5.6697e-8; epsilonp=0.95;%plate emittance epsil...

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Why do I have a never ending loop ?
The initial condition at t = 0 seems to be T = 4 for all x in your code. But you must set boundary conditions for T at x = 0 an...

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Multi objective optimization for genetic algorithm showing out of bound solutions.
If you plot x(:,2) against x(:,1), you will see that both respect the bounds you prescribed: figure(2) [x1,idx] = sort(x(:,1))...

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Please help to solve the error in evaluating a system of odes using ode45
Rho_net is an array of length 365, but it must be a single scalar value in ode_2. If you want to evaluate the array at time t g...

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Solving the differential equation by the Runge-Kutta method (ode45)
[t, y] = ode45(@odefun2,[0 3],[1,0]); plot(t,y(:,1)) function dfdt = odefun2(x,y) w = 2e16; r0 = 30e-6; c = 3e8; ...

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Breaking down a numerical integration into two parts
I1 = dx/2 * f(x0) + dx * sum_{i=1}^{n-1} f(xi) + dx/2 * f(xn) I2 = dx/2 * f(xn) + dx * sum_{i=n+1}^{n+m-1} f(xi) + dx/2 * f...

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simple x.y plot
Use y = (4*(x.^2)*log(6))+(5*(x.^2)) ./ sqrt (cos(x).^2) +1 instead of y = (4*(x^2)*log(6))+(5*(x^2)) / sqrt (cos(x).^2) +1...

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I'm receiving this error: "Incorrect number or types of inputs or outputs for function int." when trying to run the following code. I think because of the symbolic variables
syms a1 a2 a3 a4 theta dzdx = a1*pi*cos(.5*pi*(1-cos(theta))) + 2*a2*pi*cos(pi*(1-cos(theta))) + 3*a3*pi*cos(1.5*pi*(1-cos(the...

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Assumptions are not being considered in symbolic math.
What is rank(A) ? If it's 8, your system of equations has a unique solution, and you can't assume anything about it.

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Need help to fit the data without error.
I assumed you start integration at x = 5.3571429. You will need to specify dr/dx and dtheta/dx in the y0-vector below. rData =...

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Do ODE solvers use location of root of event function in its solution even if integration isn't specified to stop?
You will have to tell the solver to return control to the calling program once the corner point is reached. From there, you can ...

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How to debug this? Not getting into it. Need help
Use fit = lsqcurvefit(@(params, x) funr(params, x), initialGuess, rData(:,1).', rData(:,2).'); fit2 = lsqcurvefit(@(params, x)...

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role of flux f in bcfun of pdepe for systems of PDEs
This multiplication is nowhere performed within "pdepe". But if you look at the pdepe code below, the cases where q = 0 and q di...

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