Answered
Solve double integral using 'integral2'
y = sqrt(100-x^2-z^2) or y = -sqrt(100-x^2-z^2) -> I = integral_{x=0}^{x=10} integral_{z=0}^{z=sqrt(1-x^2)} (x+sqrt(100-...

8 years ago | 0

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Answered
Numerically stable implementation of sin(y*atan(x))/x
By L'Hospital, lim (x->0) sin(y*atan(x))/x = y. Thus define your function to be y if x=0 and sin(y*atan(x))/x if x <> 0. ...

8 years ago | 1

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Answered
How to plot a differential equation?
function main % call root finder estimate0 = 1.0; estimate = fzero(@cycle,estimate0); % call bvp4c for fin...

8 years ago | 0

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Answered
How can I fix this problem
for i = 1:numel(C) F = [A, B, C(i), D, E]; G{i} = roots(F); end Best wishes Torsten.

8 years ago | 0

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Answered
Solving trigonometric equations as a optimization problems
function fcost=cuptpc(x) L = 22.5e-6; A1 = 40; A2 = 40; A3 = 40; n=1; f=20e3; M = 1.0; / ???? A = 1...

8 years ago | 0

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Answered
Solve double intergral ?
sol=integral2(@(x,y)x+y+sqrt(100-x.^2-y.^2),0,10,0,@(x)sqrt(100-x.^2)) Best wishes Torsten.

8 years ago | 0

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Answered
optimization with integer constraints
https://de.mathworks.com/help/optim/examples/mixed-integer-quadratic-programming-portfolio-optimization.html Best wishes T...

8 years ago | 2

Answered
Need help on loop for an ODE function
t=0.01:0.01:20; for i=1:numel(t) solinit = bvpinit(linspace(0,1,10),[0,0]); sol{i} = bvp4c(@(y,u)ex1ode(y,u,t(i))...

8 years ago | 0

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Answered
I would like to know how to implement a bivariate normal distribution.
rhoR=0.5; fun=@(x,y)1/(2*pi*sqrt(1-rhoR^2))*exp(-1/(2*(1-rhoR^2))*(x.^2-2*rhoR*x.*y+y.^2)); intfun=@(R)integral2(fun,-In...

8 years ago | 1

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Answered
Hi, is this the right code for the pde (∂u/∂t= 2 + (∂^2 u)/(∂x^2 )) with boundary conditions of 0.5 and 3.5 and initial condition of x^2 - 0.5 where x ranges from -1 to 2?
It's more usual to define c = 1; f = dudx; s = 2; instead of c = 1; f = 2*x + dudx; s = 0; but the c...

8 years ago | 0

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Answered
Hi, I keep getting the error "Error using pdepe (line 293) Spatial discretization has failed. Discretization supports only parabolic and elliptic equ.." Please help it's urgent, the pde I'm trying to solve is (∂u/∂t= 1 + (∂^2 u)/(∂x^2 )). Thank you!
function [pl,ql,pr,qr] = pde_boundary_cond(xl,ul,xr,ur,t) instead of function [pl,ql,pr,qr] = pde_boundary_cond(xl,xr,...

8 years ago | 0

Answered
Evaluating polynomial at a certain x point to find y?
coeff{i} = polyfit(volHotLiq, volIce, i); if i==4 p_15 = polyval(coeff{i},1.5); end

8 years ago | 1

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How can I solve non-linear equations ?
help fsolve Best wishes Torsten.

8 years ago | 0

Answered
How to optimize a function?
x1=0; x2=20; fun=@(x)x^2+2x-3; x = fminbnd(fun,x1,x2)

8 years ago | 0

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Answered
Solve integral for x with x as bound and part of the integrand
a=0.2; b=10; c=-10; d=15; mu=3; sig=1; Pdf=@(x)1/(sig*sqrt(2*pi))*exp(-(x-mu).^2/(2*sig^2)); Cdf=@(x)inte...

8 years ago | 0

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Answered
lsqnonlin output only converging towards function in increments of length(x0)+1
lsqnonlin needs the derivatives of your functions with respect to the parameters. Thus "myObjective" is called with almost the s...

8 years ago | 1

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Answered
Polyfit with odd powers only?
x = [ ... ]; y = [ ... ]; x = x.'; y = y.'; n = 5; % degree of polynomial p ; n must be odd A = []; ...

8 years ago | 1

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Answered
Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 2-by-1.
Allocate "gamma_element" before you enter the loops: gamma_element = zeros(2,2^9); for i=1:10 ... Best wishes ...

8 years ago | 0

Answered
second order ode45-where to put boundary and initial condition?
u(r) = -1/(16*B)*dp0/dz*(1-r^2) If the analytical solution is not what you want, use "bvp4c" instead of "ode45". Best wi...

8 years ago | 0

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How to add variable to ode45 method?
The actual longitudinal coordinate z is transferred to your function "fun" by ODE45: function f=fun( *z*,p) You can...

8 years ago | 0

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Answered
BVP solver with an array of initial conditions
solinit = bvpinit(linspace(xlow,xhigh,10),@init); function yinit = init(x) yinit = [ x 1-2*x ]; Be...

8 years ago | 0

Answered
How to use bvp4c for boundary value problem with 2 unknown parameters?
fprintf('For r=%4.2f a= %4.2f \n',sol.parameters); Best wishes Torsten.

8 years ago | 0

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Answered
Does anyone could help me out with this RK4 code, the code runs but it does plot nothing
function rungekutta h = 0.1; %tama?o de paso aleft = 0; aright = 1; n = (aright-aleft)/h; %cantidad de subinterva...

8 years ago | 0

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Answered
How to discretize variables related by a formula?
n=10; X=1:n; Y=sin(X) Best wishes Torsten.

8 years ago | 1

Answered
How to use numerical solution in differential equation?
Use MATLAB's "diff" on the array of p-values to approximate dp/dz: https://de.mathworks.com/help/matlab/ref/diff.html Best...

8 years ago | 0

Answered
Optimizing ODE parameter to make solution fit empirical observations
[t,y] = ode15s(@(t,y)myModel(t,y,k0),Time,y0); function dydt = myModel(t,y,k) dydt = k; Best wishes Torsten.

8 years ago | 1

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Answered
What is the difference between function and objective function in MATLAB ?
No difference - "objective function" is just the terminus technicus for the function you want to maximize or mimimize in optimiz...

8 years ago | 1

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Answered
How can i find theta and polarplot a function for rho > 0.
theta=pi/21:0.1*pi/21:5*pi/21; rho=1-2*cos(7*theta); polarplot(theta,rho)

8 years ago | 0

Answered
bvp4c or ode45?
If you know $p_0|_{z=1}=1$ and $p_1|_{z=1}=0$ and you want to know $p_0'|_{z=0}$ and $p_1'|_{z=0}$, you don't need a shooting me...

8 years ago | 1

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Answered
Solve 4 equations with 3 unknowns
Cd=...; Z=...; fun=@(x)[1-x(1)-Z*x(1)*x(2);1-x(2)-Z*x(2)*(x(1)+x(3));-x(3)+Z*x(2)*(x(1)-x(3));-Cd+Z*x(2)*x(3)]; lb=[0...

8 years ago | 0

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