Answered
Forward, Reverse finite difference question
x = 0:0.1:1; f = @(x)x.^2; derf = (f(x(2:end))-f(x(1:end-1)))/0.1; hold on plot(x(2:end),derf); % backward plot(x(1:end-...

2 months ago | 1

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Answered
Time interation error while trying to solve a partial differential equation which describes pore diffusion resistance combined with with surface kinetics.
One error, one problem: The error: qr = De; must be replaced by qr = 1; because the boundary condition is given by p+q*f =...

2 months ago | 0

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Answered
Numerical differentiation and integration
t = [0,5:10:115]; s = [0, 4892.3, 14041.3, 22371.3, 29926.1, 36764.4, 42965.4, 48634.8, 53910.3, 58961.8, 63981.6, 69165.5, 74...

2 months ago | 0

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Answered
error in runge kutta -Unable to perform assignment because the left and right sides have a different number of elements.
You always have to use the variables at the ith time step, not the complete array in the assignments. I didn't check your compl...

2 months ago | 0

Answered
How to plot the temperature unit which is small circle raised at the left of C upper case?
Maybe by adding the interpreter ? In R2024b, your title is correctly plotted without any modifications. x=0:0.1:1; y=x.^2; pl...

2 months ago | 0

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Answered
The method of how to calculate the FWHM.
xmax = 0; ymax = 4; x = xmax:0.01:3; f = -x.^2 + ymax; FWHM = 2*interp1(f,x,ymax/2) Or directly use the inverse function of...

2 months ago | 0

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Answered
How to make my code run faster
Maybe your system does not have a solution. sol = fsolve(@fun,[1 1 0.1]); fun(sol) sol = 1./sol function equations = fun(par...

2 months ago | 0

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Finding more than one root for nonlinear equation
Equations (5) and (6) are two linear equations in q_t, beta and q_dot_b. Use them to express q_t and beta as linear functions o...

2 months ago | 0

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How would I Solve this System of Trigonometric Equations for Inverse Kinematics?
Solve eqn2 for t1 Insert the result for t1 in eqn1 and solve for t2 Insert the result for t2 in eqn3 and solve for d1

2 months ago | 0

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How to convert a fourth-order ordinary differential equation into a system of first-order ordinary differential equations in order to solve it.
If all conditions are given at x = 0, it's an easy problem: Define z(x) = integral_{x'=0}^{x'=x} d*sqrt(1+y'(x')^2) dx' The ...

2 months ago | 1

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Answered
How can I correctly implement this Meijer G-function in MATLAB for the given equation with specific parameters ?
a,b,gamma,y1 and y2 are given as numerical values ? Then use a = ...; b = ...; ggamma = ...; y1 = ...; y2 = ...; a1 = -y1...

3 months ago | 0

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Answered
How to solve a five equations systems to get the five unknown
Directly use the five experimental values (T_exp,theta) as numerical data and "lsqcurvefit" or "fmincon" to solve for the five u...

3 months ago | 0

Answered
piece wise function for thermal properties in PDE solver
When creating the geometry for your problem, I'd already take into account these two spatial regions where the different thermal...

3 months ago | 0

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Answered
Netwon algorithm with backtracking is failing
rng('default') n = 2; m = 20; c = sym('c',[n 1]); A = sym('A',[m n]); b = sym('b',[m 1]); x = sym('x',[n 1]); f = c.'*x - ...

3 months ago | 0

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Answered
Averaging specified number of points around the minimum value
data(ix-5:ix-1) are the 5 points left to the minimum, data(ix+1:ix+5) are the five points right to the minimum. So the code sho...

3 months ago | 1

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Answered
Can anyone help me to run this coding?
OdeBVP returns NaN for ff(3) at the start (see above). You will have to find out the reason (initial values for y, x, parameters...

3 months ago | 0

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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...

3 months ago | 0

Answered
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...

3 months ago | 2

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

3 months ago | 1

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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)

3 months ago | 0

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Answered
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 ...

3 months ago | 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...

3 months ago | 0

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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...

3 months ago | 1

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Answered
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 -...

3 months ago | 1

Answered
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 ...

3 months ago | 0

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Answered
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...

3 months ago | 0

Answered
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...

3 months ago | 0

Answered
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.

3 months ago | 1

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Answered
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 % ...

3 months ago | 3

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

3 months ago | 0