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Trying to create code which solves a BVP using a second-order finite difference scheme and Newton-Raphson method
% Code to calculate the solution to a % nonlinear BVP with Dirichlet and Robin BCs % Some physical parameter. mu = 10; % De...

1년 초과 전 | 0

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finding the value at a specific time from second-order ODE
The easiest (maybe slightly inaccurate) way is to use interpolation: f_conv = interp1(time,x,2.5) f_ode45 = interp1(time,y(:,1...

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Inverse fft doesn't match analytical formulation
syms w F = 1/w^2; ifourier(F); disp(char(ans))

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How do I convert symbolic values to numerical for uitable ?
syms x f = x^2-2; xsol = solve(f==0) class(xsol) xvpa = vpa(xsol) class(xvpa) xnum = double(xsol) class(xnum)

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I am getting the error message "unable to find symbolic solution" using dsolve.
What exactly am I doing wrong? Nothing. "dsolve" is simply not able to find an analytical solution because the problem is too ...

1년 초과 전 | 0

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I keep getting the "not enough inputs error" and I don't know how to fix it
m1 = 135; m2 = 30.3455; w1a = .220; w1w = .780; w1m = .000; w2m = .202; w2w = .798; w2a = .000; syms x [6 1]; F(1) = w1...

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Nonlinear constraints depend on the output of optimization objective
Define the constraints using a lower bound of 0 for x(1) (you can prescribe this in the array lb) and one linear constraint (you...

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Solving ODE with explicit equations
If you have a mixture of differential and algebraic equations, you need to define the mass matrix appropriately. In your case -...

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Error in running the Example script of pdepe
As you can see, the code runs under MATLAB R2024b (and should be no problem under R2023b, too). I suggest contacting Technical ...

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How to optimize an reduce the computation time
I don't understand the sense of your while-loop. If you want to define Psat as a function of fg, the problem becomes more compl...

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How to convert symbolic expression to numeric?
integrand_num = matlabFunction(subs(simplify(integrand))) gives you a function handle with y as input argument (see above). A...

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Concerned that matlabFunction( ), when converting from symbolic to numerical, changes the sizes of matrices and vectors,
As you can see M = reshape([...],[3 3]) Thus the expression in [ ] is 1x9, but it is finally reshaped to 3x3.

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Cannot subtract number of order smaller then e-4 from variable
It's just a question of how the numbers are displayed. Internally, the precision of computing is much higher. format long % ...

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Reduce the size of Matrix from 100x100 to 35x11
x1 = x1(1:35,1:11)

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best combination for lowest possible dose and lowest possible material cost
You mean bestDoseRate = Inf; bestCost = Inf; for index = 2:9261 if (mixDoseRate(index) <= bestDoseRate && mixCost(index) ...

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RK4 help (someone help fix this)
Use for i=1:n_nodes-1 instead of for i=1,n_nodes-1;

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Solving a set of complex trig equation
Do you see the problem ? Your R-values and your y- and z-values are not compatible (at least for n = 3). It must hold that R_v...

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Warning: Non-finite result. The integration was unsuccessful. Singularity likely. > In integral2Calc>integral2t (line 131)
fun(Phi0(1),Phi0(1)) gives NaN + 1i*NaN

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How to solve rachford - race function using newton method
Multiply the equation by product_{i=1}^{n_c} (1+f_Rg*(K_i-1)). This gives you a polynomial of degree n_c-1 in f_Rg which can be ...

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How can I evaluate the transition matrix using the fourth order Runge-Kutta ODEs
If it's still of interest: this code seems to work correctly. I don't know why using n = size(A,1); E = A(t+dt/2)*(eye(n)+dt/2...

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Why do I receive error using BVP5C "The boundary condition function BCFUN should return a column vector of length 1"?
You have one first-order ODE, but two boundary conditions. That's mathematically impossible - you can impose only one condition....

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Event function and ODE.
Don't use both events simultaneously in your event function. Start the solver with the first event function and integrate until...

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Trouble solving system of pdes with pdepe
"pdepe" is a solver for parabolic-elliptic partial differential equations. The positions with zero elements in the f-vector indi...

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Solving the differential equation gives unexpected results. How to fix that?
Better ? v(t) = v(0) - g*t - v0*log(m0/(m0-k*t))

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Define function for transient transient boundary condition
F1= 3.843e-8; F2= -3.482e-5; F3= 1.179e-2; F4= -1.95; F5= 23.69; Trefrig = @(location,state)F1*state.time^4 + F2*state.time...

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How to write an event function to stop at second or third x axis crossing.
I'd make the solver stop at each x-crossing. After it returns control to the calling program, add 1 to the number of crossings a...

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Why don't I need a comment character after an (...) ellipsis?
Most probably there is the convention that ... is the symbol to connect two subsequent lines and that everything behind the ... ...

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AYUDA EN CODIGO DE MATLAB PARA UN ESTRUCTURA DE PUNETE EN 3D
If you insert the lines % Calcular desplazamientos en los grados de libertad libres rank(K_aa) size(K_aa) before the command...

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Why Is Colon Operator Not Equivalent To linspace Command?
Both arrays seem to be generated differently such that floating point issues come into play: z1 = 0:.08:50000; z2 = linspace(0...

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How to draw the function relationship graph between two or three variables, where these variables are solved by a system of equations.
Here are the three possible solutions for VL given tc. % 定义符号变量 VL=20; syms tc t2 Q_out Vco Vcn VL %参数关系 L=100e-9; C=50e-6...

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