How can I solve a system of partial differential equations?
Use a first-order difference quotient to discretize dT_f/dz in space and use ODE15S to solve the resulting system of ordinary di...

6 months ago | 0

how to generate random point inside a sphere
R = 3; % radius of the sphere Xc = 4; Yc = -4; Zc = pi; % (Xc,Yc,Zc) center of the sphere rval = 2*rand(1)-1; elevation...

6 months ago | 0

How to find the name of a function for a known value?
Textedit the code and search for the string '0.98'.

6 months ago | 0

| accepted

SpecifyCoefficients for a specific PDE
https://de.mathworks.com/help/pde/examples/heat-distribution-in-a-circular-cylindrical-rod.html

6 months ago | 0

| accepted

R2 approximation error as in Excel
https://de.mathworks.com/help/stats/coefficient-of-determination-r-squared.html

6 months ago | 0

Creating new matrix from the second column of other matrices
new_matrix = [PIV_1(:,2),PIV_2(:,2),...,PIV_10918(:,2)] Quite much to write ... You should have worked with one 10918x1000x4 ...

6 months ago | 0

Generate Independent Identically and Lognormally Distributed Random Variables
Note that mu and sigma you supply for "lognrnd" are not mean and standard deviation of the underlying lognormal distribution, bu...

6 months ago | 0

| accepted

Why do I get the error “Dimensions of arrays being concatenated are not consistent.”?
T = [ cos(d), -sin(d)*cos(b), sin(d)*sin(b), a*cos(d); sin(d), cos(d)*cos(b), -cos(d)*sin(b), a*sin(d); 0, sin(b),...

6 months ago | 0

| accepted

Generating random variable from certain standard deviation and mean
n = 100; x = 0.3*randn(n,1) generates 100 normally distributed random numbers with mean 0 and standard deviation 0.3.

6 months ago | 1

How to compute numerical gradient of an unknown function in matlab Simulink?
The i'th component gi of the gradient vector g is approximately given by gi = (f(x1,...,xi+h,...,x10)-f(x1,...,xi,...,x10))/h ...

6 months ago | 0

Having Trouble Using For-Loop Over Distributed Range with ODE45
delta1 = @(t) (t<=1200) delta0 = @(t) (t>1200) ODE = @(t,x,gamma,psi,beta) [delta1(t)*(-gamma)*x(1) + delta0(t)*psi*x(1); beta...

6 months ago | 3

| accepted

Substitution of initial numerical values before odefunction
Use "matlabFunction" to convert every symbolic input to ODE45 into numerical function handles before calling ODE45.

6 months ago | 0

| accepted

How do I maximise Volume of a cylinder such that its Surface Area is less than 10 using fmincon by predicting only either radius or height but not both?
Not possible. Since r and h are interdependent, "fmincon" must be able to vary both and thus predict them simultaneously. Of co...

6 months ago | 0

| accepted

How to fix "Index exceeds the number of array elements (1)"?
for i=1:length(L) psi0= psi(i); L0 = L(i); To=[cosd(psi0) sind(psi0) 0; -sind(psi0) cosd(psi0) 0; 0 0 1]; Tg=[To ze...

6 months ago | 1

How to fit multivariable equation?
coeffs = [inputs, ones(size(inputs,1),1)] \ outputs

6 months ago | 0

I need help in this question please?
y(t) = sum_{i=0}^{Inf} a_i*t^i y'(t) = sum_{i=1}^{Inf} i*a_i*t^(i-1) y''(t) = sum_{i=2}^(Inf} i*(i-1)*a_i*t^(i-2) Set y''(t)+...

6 months ago | 0

How to calculate the (odd ,even) condition in the following Poisson distribution for p_z parameter? i need some help in the code bellow
function main p1 = 0.9; p2 = 0.8; q1 = 1-p1; q2 = 1-p2; z = 6; vec = zeros(1,z); vec(1:2:end) = q1/p1; v...

6 months ago | 1

Lagrange Interpolating Polynomials using Matlab
You must use a fitting tool, not an interpolation tool to solve your problem. Apply "polyfit" with x-values = Generation Output...

6 months ago | 0

| accepted

CDF of rain rate
https://stackoverflow.com/questions/36385036/how-to-make-a-cdf-from-a-histogram-in-matlab

6 months ago | 0

How to define a variable as an integer that's equal to or greater than zero?
rest = mod(struct_idx,4); if rest == 1 ... elseif rest == 2 ... elseif rest == 3 ... elseif rest == 0 ... end

6 months ago | 0

| accepted

Matlab code for delay differential equations
https://de.mathworks.com/help/matlab/delay-differential-equations.html

6 months ago | 1

| accepted

How to solve this equation which contains complex number, bessel equation and its derivative?
x0 = [2; 1]; fun = @(x)[real(1i*besselj(1,complex(x(1),x(2)))-complex(x(1),x(2)).*(besselj(0,complex(x(1),x(2)))-besselj(2,...

6 months ago | 1

Finite difference method - solving boundary conditions
y1(1) - 1.0 = 0 (y1(i+1)-2*y1(i)+y1(i-1))/dx^2 - (2*(y1(i+1)-y1(i-1))/(2*dx)/(1-x(i)) + y1(i)/(x(i)^2*(1-x(i))^2)*(y1(i)^2-1+(y...

7 months ago | 0

| accepted

How to enforce ode15s to solve a DAEs system with some state variables limited by a range?
The solution of your problem is uniquely determined by the equations you impose - you can't impose any further conditions on the...

7 months ago | 0

| accepted

Solving boundary value problem for nonlinear differential equation using method of collocation - Gauss sites
Up to my experience, the FORTRAN code "colnew" and "colsys" developed by Ascher are still the best bvp solvers available. Searc...

7 months ago | 0

| accepted

How to solve a set of DAEs with multiple dependent differential variables
The Euler equations are not thus easy to solve. You should consult a book on numerical methods for the equations of gas dynamic...

7 months ago | 0

Boundary condition in non-linear ODE
function du = ode4(eta,u) theta = u(1); Sr = u(2); % beta dtheta = u(3); % d(theta)/dr ...

7 months ago | 1

| accepted