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How are initial values chosen for either lsqcurvefit or nlinfit functions?
There must be some mathematical operation within your objective function that gives Inf, NaN or something similar (e.g. division...

8 years ago | 0

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differentiation for a function
syms x y(x) diff(x-y^2,x) Best wishes Torsten.

8 years ago | 0

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how to stop dde23 when one of states reach certain value?
Use the "Events" option of dde23. Best wishes Torsten.

8 years ago | 2

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How to set open boundary conditions with Pdepe for advection-diffusion-reaction of concentrations?
Choose your interval where you solve your equations big enough. This way, you won't come into trouble with the boundary conditio...

8 years ago | 1

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Answered
simultaneous fitting of two plots with two functions
xdata=[x(:,1); x(:,1)]; ydata=[y1(:,1); y2(:,1)]; fun=@(x,xdata) [f1(xdata(1:numel(xdata)/2),x(1),x(2),x(3),x(4)); f2(x...

8 years ago | 0

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simultaneous fitting of two plots with two functions
Use "lsqcurvefit" with the data set xdata = (x,x),ydata = (y1,y2). Best wishes Torsten.

8 years ago | 2

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Answered
Is it possible to use DuDx as boundary condition in pdepe if DuDx doesn't appear in the equation in a system of PDE/ODE?
Mathematically, an ODE does not need a boundary condition - the value of an ODE in a boundary point is given by solving the ODE ...

8 years ago | 1

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Answered
1st order differential equation , boundary conditions
syms y1(t) y2(t) eqn = [diff(y1,t) == y2*y1*log(450/y1), diff(y2,t) == 0]; cond = [y1(0)==40, y1(15)==95]; [y1Sol(t) ...

8 years ago | 0

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Answered
1st order differential equation
This is a boundary value problem - use "bvp4c" instead of "ode45". Or try "dsolve". Best wishes Torsten.

8 years ago | 0

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Problem of integral combined with fzero
Instead of specifying a point (0.01) in the call to "fzero", you should specify a search interval which excludes the point c0=0....

8 years ago | 0

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Answered
could anyone help me to solve the issue in the following code
X=[3] for t=1:length(X) A = partitions([X(t)]) for d=1:length(A) if length(A{d})>1 for e=1:leng...

8 years ago | 1

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Answered
How can I solve a system of differential equations of second order?
Write your system as w1' = w2 w2' = k*(w4*B3(w1,w3,w5)-w6*B2(w1,w3,w5)) w3' = w4 w4' = k*(w6*B1(w1,w3,w5)-w2*B3(w1...

8 years ago | 0

Answered
CDF and Inverse CDF of Wrapped Cauchy Distribution
function main p = linspace(0,1,11); prob = linspace(0,1,100); x = zeros(numel(p),numel(prob)); for ...

8 years ago | 1

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Answered
matlab pdepe boundary conditions help
"pdepe" is a solver for parabolic/elliptic partial differential equations of 2nd order. Your equations are hyperbolic equations ...

8 years ago | 0

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Multiple parameters optimization having calculated and experimental values
function main P_k = ...; Hcexp = ...; T_k = ...; z = ...; w = ...; v = ...; c = ...; a...

8 years ago | 1

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Answered
How to find the exact solution of heat equation U_t=U_xx bc U(0,t)=0=U(1,t), U(x,0)=sin(pix). Also Matlab code?
Easy: fun = @(x,t)sin(pi*x).*exp(-pi^2*t); x = linspace(0,1,50); t = [0.0 0.1 0.2]; [X,T] = meshgrid(x,t); U = ...

8 years ago | 0

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Create a vector z with 1000 elements generated by the rand-function. The generated values must have a mean value of 0.5 (mean(0.5)). And a standard deviation of sqrt(1/100*12), (std(x)).
0.5*(a+b) = 0.5 1/12*(b-a)^2 = 0.12 Solve for a and b. This will give you the interval [a b] for which you must gener...

8 years ago | 2

Answered
Differential Equation with Coefficients as Integral Functions
fun=@(x,y)[y(2);-y(2)*integral(@(z)z.^2+3*z-1,0,x)]; is a suitable function to be used with ODE45, and it represents your d...

8 years ago | 1

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Answered
calculating sum of an array by using if-or statement in matlab
Deger = [20 25 27 28 31 32 33 34]; Node1 = [1 2 5 6 7 4 3 3]; Node2 = [2 5 6 7 4 3 2 6]; minimum = min(min(Node1),min...

8 years ago | 0

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Answered
how to define an integral function
fun=@(z)z.^2+3*z-1; F=@(x)integral(fun,0,x); F(10)

8 years ago | 2

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Answered
Square of 20 random number sum up to 1
r = r / sqrt(sum(r.^2)) Best wishes Torsten.

8 years ago | 0

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How to fit a curve with negative powers of x
If you want to fit parameters a0,...,an to a function of the form y = a0 + a1*x^(-1) + a2*x^(-2) + ... + an*x^(-n) you c...

8 years ago | 0

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could anyone help me how to write the bell number equation in matlab
nfinal = 10; b(1)=1; for i=2:nfinal+1 b(i)=0.0; for j=0:i-2 b(i)=b(i)+nchoosek(i-2,j)*b(j+1) end ...

8 years ago | 0

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Answered
Coupled differential equation system
Write your system as L11*di1/dt+L12*di2/dt+L13*di3/dt = v-r*i1 L21*di1/dt+L22*di2/dt+L23*di3/dt = v-r*i2 L31*di1/dt+L...

8 years ago | 0

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Answered
How can i minimize a function provided that another function is greater than 0?
Use "nonlcon" to set the constraint sum(2000*(1/(2*5))*((first(A)-D*[2:7]).^2-(first(A)-D*[1:7-1]).^2)) >= 0 Best wishes...

8 years ago | 1

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Answered
How can I multiply 4D array? Optimization assignment problem
Use "reshape" to turn your 4d-matrices into an 1d-vector, multiply the vectors componentenwise and sum.

8 years ago | 0

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Answered
How to have Ode45 display an answer to an array input?
I changed the ODE, but the way to solve an equation for several parameters should become clear. function main nt = 11; ...

8 years ago | 0

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Is there any mistaken on my fmincon solve?
fmincon works with arrays, not with scalar variables. Thus you have to place your scalar variables to be optimized (dec_val, acc...

8 years ago | 1

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Answered
MATLAB event function help
function main tRange = [0 10]; Y0 = [0 20]; options = odeset('Events',@event_function) [tSol,YSol,te,ye,ie] =ode45...

8 years ago | 0

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Answered
Help needed with while loop code
while RF_tot<=8 && D_var <= 30 D_var=D_var+1 RF_tot=RF_tot+RF(D_var) end Best wishes Torsten.

8 years ago | 0

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