# Torsten

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**Content Feed**

Interpolating data to get values at specific depth

Make X and Y also 224x164x37 (just by repeating the planar profile 37 times) and use interp3 to interpolate to the depth of your...

ongeveer 11 uur ago | 2

| accepted

Solving nonlinear system of PDE by using finite difference method for spatial and RK4 for time derivative?

You need two boundary conditions for Tap, one boundary condition for Tsg and one boundary condition for Tag. Your equation for ...

1 dag ago | 0

PDE solve with bvp4c

Take a look here on how boundary value problems with two regions (in your case -1 to 0 and 0 to 1) have to be set up for bvp4c: ...

2 dagen ago | 0

Solve a system of nonlinear differential equations

Define the unknown functions as y(1) = F, y(2) = dF/dx, y(3) = G, y(4) = dG/dx, y(5) = H. Then the equations are dy(1)/dx = y(...

2 dagen ago | 1

I need some help to solve non-linear equation with three unknowns and three knowns with having 170 different values for one known.

M = [eta+1,Rz,-Ry;-Rz,eta+1,Rx;Ry,-Rx,eta+1]; M = repmat(M,170,1); b = []; for i = 1:170 b = [b;Xw(i)-Tx;Yw(i)-Ty;Zw(i)-Tz...

3 dagen ago | 0

How can I skip the rest of an if statement?

Also in for-loops, "break" only exits the inner structure, but the outer loop runs until the end (see below). Thus you cannot ...

3 dagen ago | 0

Surface plot doesn't correspond to optimization solution

The problem is now, when I select a point randomly in the surface plot, and then calibrate the model for these values, I do not ...

3 dagen ago | 0

| accepted

Solving an equation with symbolic matrix

https://uk.mathworks.com/matlabcentral/answers/1918100-error-using-solve-with-symmatrix-equation

4 dagen ago | 1

A group of 12 people all roll a pair of dice 12 times, how often does each person roll a total number that is greater than or equal to 7?

In my opinion, it should be roll1=randi(6,12); roll2=randi(6,12); total=roll1+roll2; GT7 = total>=7; totalGT7 = sum(GT7,1);...

4 dagen ago | 1

| accepted

error in for loop

u(j-3) is only defined for j>=4, u(j+3) is only defined for j<=length(R)-3. Similar restrictions hold for the other indices. Thu...

4 dagen ago | 0

I'm suppose to plot the response of the system but i'm getting wrong values

alpha is a constant , and this is the value of it , I doubt that the rate of change at t=0 for x(5) should be 2.55e17 as you g...

5 dagen ago | 0

How can I multiply a row vector with each of two column vectors?

t = [1 2]; s = [(1:3)',(4:6)']; kron(t,s)

5 dagen ago | 3

final value of x in PDE

i want to solve this equation for r at given time and concentration I assume that the time for which you want to get r is in th...

6 dagen ago | 0

How to prevent substrate concentration going below minimum limit in fed batch fermentation model.

You can use the "Events" option of the ode integrators to interrupt and restart integration with different settings if a certain...

6 dagen ago | 0

| accepted

How can I ensure that the initial solution (x0) for fsolve does not result in Inf or NaN values?

You know your "external_fun" best. Try to deduce in advance which inputs will lead to failure. Maybe you can use "lsqnonlin" ins...

7 dagen ago | 0

Huge minimum value from expected results

I cannot run this code because it takes too long or maybe the matrix exponential cannot be computed analytically. Does it give ...

7 dagen ago | 0

| accepted

ODE45 solver returning constant value as the input variable.

As you can see when you run the below code, p is in the order of 1e12 which makes dL/dt effectivly 0. Check your units. %Def...

7 dagen ago | 1

| accepted

The code does not converge

I seems your function does not vary much with rho. The evaluation cannot find a value for rho for which the function has a zero....

7 dagen ago | 0

| accepted

How to plot the error of two numerical methods on the same graph?

%% Given data f=@(x) 8-4.5*(x-sin(x)); df=@(x) -4.5*(1-cos(x)); x0=1; tol=0.0001; n=50; [x_newton,i_newton,Error_newton]=n...

7 dagen ago | 1

Modifying the objective function in order to meet the optimization variable boundaries

if (A <= 1e-04) & (A >= 4e-04) How can A be <= 1e-4 and >= 4e-4 at the same time ? And if-statements have to be done elementwi...

9 dagen ago | 0

Solve a matrix equation

D = eig(A) will give you the values for D for which det(A-DI)=0

9 dagen ago | 0

| accepted

Solving goal programming problem with MATLAB

x0 must be a vector of size 1x5, not 1x4. Further, your function must return a vector of length 4, not 3. Further, the first o...

9 dagen ago | 0

plot() and fplot() give different results for the same function

x = linspace(0, 100, 10000); y = 2*sqrt(1+x)+sin(sqrt(pi)*x).*sin(sqrt(1+x)*pi).*(2*x+1)./sqrt(x) - 2*sqrt(1+x).*cos(sqrt(x)*pi...

9 dagen ago | 0

Vpasolve can not find a solution that I know it exist

Maybe it must read Eq2 = ((a21*W2)/(c2*(a21+a22))) - x12 == 0; instead of Eq2 = ((a12*W2)/(c2*(a21+a22))) - x12 == 0; ? c...

9 dagen ago | 0

| accepted

How to build a graph of the solution of a second-order differential equation in MATLAB

Since sin(pi) = 0, your differential equation reduces to y'' + y = 0 with general solution a*sin(t) + b*cos(t) Now incorpor...

9 dagen ago | 1

"Busy" when running this code with ODE45

Use ode15s instead of ode45 - you have a stiff system of differential equations.

10 dagen ago | 0

How to solve complex equations?

Your equation has only complex solutions. Note that you used sind instead of sin in the function definition. Thus assuming the...

11 dagen ago | 1

| accepted

how to output quantities involving time derivatives in pdepe

You don't have access to the spatial discretization of pdepe, thus no access to the exact time derivatives. But if you choose th...

11 dagen ago | 0

| accepted

lsqcurvefit claiming complex-valued function

Although the fiting function fit_function is the log of a real valued part of the function, why is it considering that the funct...

11 dagen ago | 0

How to test whether a function has roots within a given range?

F = @(x) sin(x); xmin = 0; xmax = 6*pi; x = linspace(xmin,xmax); Fx = F(x); I = find(diff(sign(Fx))) F(x(I)) F(x(I+1))

11 dagen ago | 0

| accepted