Answered
How do i solve differential equation 2nd oder simbolically and numerically?
syms t y(t) sigma(t) eqn_diff = diff(y,t,2)+3*diff(y,t)+y(t)-2*sigma(t)==0; ysol(t) = dsolve(eqn_diff); var = symvar(ysol) e...

4 years ago | 1

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Answered
How to solve method of lines on one-dimensional heat equation using Euler's method?
% Parameters k = 0.5; % Evaluate BC dx = 0.01; x = 0:dx:1; dt = 0.0001; t = 0:dt:0.5; h = 1/(length(x)-1) ; %step size ...

4 years ago | 0

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Answered
I need help to make graphs please
See above. I added four lines to your code to plot the results and changed the line flux(index)=fluxp+fluxe0+fluxe1+fluxe2; to...

4 years ago | 1

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Answered
The proper way to sample 3 normally or lognormal distributed variables added up to 1
You can define a common probability distribution of the three variables on the triangle x + y + z = 1, x, y, z >= 0 but this c...

4 years ago | 0

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How can I constrcut this matrix for a problem?
If x = [x0,x1,...,xn] is an 1x(n+1) row vector, you could use M = zeros(n+1); for i = 1:n+1 M(i,:) = psi(x(1:n+1)-x(i)); ...

4 years ago | 0

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Answered
Are the algorithms used in mldivide direct solvers?
Are the algorithms used by "mldivide" for any input direct solvers (not matter if (not) sparse, (not) symmetric, (not) banded et...

4 years ago | 0

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how to write an equation the it is function of itself (solar cell current equation)
I guess you want to solve for J ? Then define fun_J = @(J) J - (J_PH - J0*(exp(q*(V+J*R_S)/(k_B*T))-1)-(V+J*R_S)/R_SH) and u...

4 years ago | 0

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How to write the below equation in MATLAB
R = gammainc(x/theta,k)

4 years ago | 0

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routing problem optimization code
https://math.stackexchange.com/questions/1658457/longest-path-with-constraint

4 years ago | 0

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why do I get "Array indices must be positive integers or logical values"
Most probably you mean Dnorm = Dsm./Dstd instead of Dnorm = Dsm./Dstd(D)

4 years ago | 0

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Answered
how to reduce its computing time?
Here is the code for the first loop. You can do it for the other loops in the same manner. u=[30 40 50 70]; b=u; [~,C]=size(b...

4 years ago | 0

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Answered
I have to output results (z1 and z2) so the minimum value in Z1 I want to find the value in the same index in Z2, they are 4 rows and 9 columns.
%the output of the code are 2 tables z1 and z2, each consists of 4 rows and 9 coloumns, so if the the minimum value in z1 coloum...

4 years ago | 0

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I'm not getting any output here, can anyone please tell me what's the issue here?
for i=1:(length(time)-1) instead of for i=1:(length(t)-1)

4 years ago | 0

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Automating the derivation of sensitivity indices
You could use syms beta_s alpha_a alpha_u mu q_i gamma_a eta_i eta_u beta_s_num = 0.274; alpha_a_num = 0.4775; alpha_u_num =...

4 years ago | 1

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Pdepe: Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.
At the moment, you set as boundary conditions du/dx + u*dv/dx = 0 at x=0 and x=1 Check whether this is really what you want. ...

4 years ago | 1

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Answered
solve system of equations imposing two variables not to be equal
Solution is C1 = C2 = 1 v11 = l11, v12 = l12, v21 = l21, v22 = l22 v11 = l31, v12 = l32, v21 = l41, v22 = l42 So if l11 = l...

4 years ago | 0

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Answered
hi i am trying to get the output of this loop in one matrix to use it in another function can anyone help me ?
z = acos(0.9); v = [ 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 .9 1]; % d = -z + acos(v*cos(z)) is (one) solution of (v/0.06)*tan(z)*s...

4 years ago | 0

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Answered
How to use ODE function for modelling tanks in series
xa_in = 0.3; % inital concentration of A flowing in. xa = 1.0; % inital concentration of A in the reactor 1. tend = 15; %runti...

4 years ago | 1

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Answered
Doing a nested numerical integral in Matlab
mu = -20:0.01:20; f = @(mu) integral2(@(u,sigma) sin(mu*sqrt(1-sigma.^2).*cos(pi/2*u)).*(sin(mu*sigma/2)).^2,0,1,0,1); P = arr...

4 years ago | 0

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Answered
The size of X must match the size of Z or the number of columns of Z.
Errors in coding and discretization have been corrected, I guess. Why did you delete your previous question ? Quite impolite in...

4 years ago | 0

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Solving equation with two solutions
syms M F = M*exp(-M^2/2)==0.2; vpasolve(F, [1 Inf])

4 years ago | 0

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how to save a matrix in each iteration in different variables
Before entering the outer loop, initialize "vol" as vol(nouter,11,4) where nouter is the number of outer loops and save the re...

4 years ago | 0

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How do I extract a 2-D matrix from a 3-D matrix using a row number as index
M_3d = rand(2,6,2) M_2d_1 = squeeze(M_3d(1,:,:)) M_2d_2 = squeeze(M_3d(2,:,:))

4 years ago | 1

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Answered
Limiting range of a matrix
A = [1 2 3 4 5 6 7 8]; A(A<3) = 3; A(A>6) = 6; A

4 years ago | 1

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fsolve with vectors x and y (not x(1) x(2))
%defining constants: N_mesh=3; %define the problem for fsolve problem.objective = @(z)EquationsList(z,Nmesh); %initial poin...

4 years ago | 2

Answered
I want to fit the data with the mathematical model containing numerical integration, please help me!
%AIfit.m %function par = AIFit load('GST33.mat','Expression1'); xdata = Expression1(:,1); ydata = Expression1(:,...

4 years ago | 1

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Answered
[Ask Help] - Monte Carlo Coin Flip
Add the lines E = sum(coin); M = max - E; probOf0 = M / max probOf1 = E / max to your code. But your way to generate the ...

4 years ago | 0

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dijkstra algorithm function problem
Works for me. %--------------------------------------------------- % Dijkstra Algorithm % author : Dimas Aryo % email : mr.d...

4 years ago | 0

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how to calculate a double integral with simpson rule?
If your "simpson" function accepts matrix inputs for the function values on a 2d-grid in x/y direction, you might want to study ...

4 years ago | 0

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Answered
3-D Countour Plot based on velocity data
xyzu = readmatrix('velocity3d.txt'); x=xyzu(:,1); y=xyzu(:,2); z=xyzu(:,3); u=xyzu(:,4); F = scatteredInterpolant(x,y,z,u);...

4 years ago | 1

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