Answered
Simulate Fick's 1st and 2nd laws of mass diffusion.
The correct update for inner grid points is C_new(i,j) = C_old(i,j) + dt * (D_x*(C_old(i-1,j)-2*C_old(i,j)+C_old(i+1,j))/dx^2 +...

2 years ago | 0

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Answered
Indices shown in plot are off
My guess is that the x-axis has a resolution of 10.

2 years ago | 0

Answered
issue in calculation of wave speed
The below code will at least give you the correct update of the solution. You don't initialize "half_max_positions" ; that's wh...

2 years ago | 0

Answered
Minimize difference between two data sets
Use [output] = [method](@(AB) my_func(AB(1),AB(2)), [A B]) instead of [output] = [method](@(A,B) my_func(A,B), [A B])

2 years ago | 0

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Answered
1D advection diffusion with pdepe
You mean something like this ? X = linspace(0, 1, 100); W = linspace(0, 2, 30); m = 0; sol = pdepe(m, @pdefun, @ic, @bc, X, ...

2 years ago | 0

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Answered
traveling waves of fisher kpp equation
Your equation reads u_{t} = - (u_{xx}+u_{yy}) + u(1-u) You miss the minus sign in your code (at least if the equation you wrot...

2 years ago | 0

Answered
Summing results at the end of a loop
x = linspace(0, 90.*(10.^-3), 100); w = [7.5.*(10.^-3),7.5.*(10.^-3),7.5.*(10.^-3)]; u = [(8.883).*(10.^-3),(8.883).*(10.^-3),...

2 years ago | 0

Answered
calculate the normal of a 3D plane
I would like to know if it is correct to calculate the normal of this plane in the following way: N = cross(P(1,:) - P(2,:), P(...

2 years ago | 0

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Answered
"Empty sym" when solving a system of linear equations with different conditions
Your system only has a (nontrivial) solution if i = 1. In this case, the solution is given as below. syms Z1A Z2A Z3A Z4A Z1B Z...

2 years ago | 0

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Answered
Temperature profile in a pipe flow with Matlab pdepe solver
I corrected as much as I could, but the computation of Q looks different in your code in comparison to the article. %% Main cod...

2 years ago | 0

Answered
Substitute partial differential into symfun
syms G(h) h(t) t Q = G(h) dGdt = diff(Q,t) % -> D(G)(h(t)) occurs s = children(dGdt) % Now define G(h) and derive: G ...

2 years ago | 1

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Answered
Using a loop to add rows to a struct, but the counter overwrites the rows.
I don't know how "trial" and "blockInfo" are organized. Here is one suggestion: for ifile = 1:3 for s = 1:nTrials struc...

2 years ago | 0

Answered
I am trying to perform a simple operation FOR loop. I think I am not able to get the indexing right.
%% why does not the following operation work Because the numbers 1,2 and 3 in t1, t2 and t3 are not indices you can loop over, ...

2 years ago | 0

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Answered
Kelvin functions ker kei functions evaluation
The value kei(0) = -pi/4 only exists in the limit : syms x a = exp(pi*1i/4); limit(imag(besselk(0,a*x)),x,0,"right") limit(i...

2 years ago | 0

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constrained optimization with Matlab, symbolic function
If your function f is symbolic, you first have to convert it to a numerical function by using "matlabFunction". k_tot = ...; a...

2 years ago | 0

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I am unable to find the minimum value of function f in this optimization problem. The solver always returns 0 for all variables which is not possible. I am unable to correct.
The solution is correct: A*x <= b is satisfied, and since all elements in the f-vector are positive, 0 is optimal. Maybe you wa...

2 years ago | 0

Answered
int function is not working properly in matlab
Evaluate gamma(n_star_D3(i)+l_d+1) gamma(n_star_D3(i)-l_d) and you will see the reason. Consequently, Gff_D3(i)...

2 years ago | 0

Answered
Negative sign produced by "functionalDerivative" - why?
As you can see here at the bottom of the page https://uk.mathworks.com/help/symbolic/sym.functionalderivative.html functionalD...

2 years ago | 0

Answered
fmincon get the wrong answer
Cost of buy with price 26 is 2*26 + c = 152 in your setting. Note that although you don't generate energy, Cg_i(0,a,b,c) = c - t...

2 years ago | 1

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Answered
Why the results of three codes with the same expression and method are different ?
Integrate equation (1) from x = 0 to x = x, and the problem will become much easier. dvdx0ini = 1; St = [0.1,0.5,1]; hold on ...

2 years ago | 0

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Curve fitting and parameter estimation with lsqcurvefit
% Load data data = readtable('infections.csv'); dates = datetime(data.Date, 'InputFormat', 'dd-MMM-yy'); cases = data.Cases; ...

2 years ago | 0

Answered
How to set lower bound lb as a function of optimization variable.
Use function "nonlcon" to define nonlinear equality and inequality constraints. If v(i) depends linearly on the solution variab...

2 years ago | 2

Answered
When using 'quadprog' how do I limit certain solutions so that they can only become whole numbers?
https://uk.mathworks.com/matlabcentral/answers/660423-can-i-solve-mixed-integer-quadratic-programming-miqp-problems-in-matlab-us...

2 years ago | 0

Answered
Synthax for equation in script
r0 = 3; r1 = 4; delta = linspace(-r0,r0,31).'; k = linspace(-r1,r1,31).'; 0.5*sqrt((delta+k.^2).^2+4*k.^2)

2 years ago | 0

Answered
Equal arc discretization method code
warning("off") syms t t1 t2 % Parameters R2 = 12; %outer radius (between this radius and R1 is constant arc increment) b = 2...

2 years ago | 0

Answered
A quatity is being solved by a self consistent integration
format long syms x A = 2000; a = 500; b = 1000; Z = 0; for i=1:20 f = x^4*((A^2+Z^2)/(A^2+4*(x^2+a^2)))^4 / (sqrt(x^2+...

2 years ago | 0

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Answered
How can I write the term \sum_{q=1}^{m} b_{pq}(t)g_q(y_q(t-\tau_{q}(t))) to produce the same graph
I don't know exactly what you are asking for, but if it's about solving Equation 1, you will have to use a solver for delay diff...

2 years ago | 0

Answered
Non linear fitting with 3 independent variables
M = load("Data.mat"); fun = @(A,B,C,E)(A - B*M.IL - C*M.a).*exp(-E*M.Vf); f = @(A,B,C,E) fun(A,B,C,E) - M.K; A0 = 13.5*13.2; ...

2 years ago | 2

Answered
Finite Difference Method - Central Difference Method for Groundwater Flow Problem
It would help if you included the mathematical description of your problem in order to compare with your coding (equation(s) to ...

2 years ago | 0

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Answered
How to return a vector output when a vector input is given to a function_handle representing a constant function?
This works in both cases: % Usual Case syms x; syms t; u = symfun(x^2,x); u_x = diff(u,x); u_x = matlabFunction(u_x); u_...

2 years ago | 0