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Solve ODE without initial condition
Your ODE is nonlinear. The symbolic toolbox is not able to find an analytical solution for it. You will only be able to solve it...

mehr als 2 Jahre vor | 0

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this is my sample code and i have to plot 8 by 8 matrix in my actual code, the code itself is correct but it is taking forever,any other way to plot this please help
w=1:3; c44 = 44; n = numel(w); y = zeros(n,1); y1 = zeros(n,1); y2 = zeros(n,1); y3 = zeros(n,1); for j = 1:numel(w) y...

mehr als 2 Jahre vor | 0

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ODE45 solving 3 equations and comparing to RK-4
%% RK4 methods %% Description % RK4 methods are used to solve coupled first-order ODEs clear close all clc %% Input vari...

mehr als 2 Jahre vor | 0

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How to check the convergence and accuracy of the Problem using BVP4c
Inf = 3 seems to be sufficient: global alpha beta Pr Nb Nt %eq1 alpha=1.2; beta=0.3; %eq2 Pr=1.7; Nb=0.1; Nt=0.1; hold o...

mehr als 2 Jahre vor | 0

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How can I plot?
syms b omega r t theta T delta b = 0.1; omega = 2*pi/5; r = b*(1+omega*t); theta = omega*t; C = [r*cos(theta); r*sin(theta)];...

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why isn't my newton rhapson method giving me a quadratic conversion rate?
If b=log(d/dI)/(2*kw); instead of b=log(d/dI)/2*kw; as was first written in your previous code, then B must also be B=(log(...

mehr als 2 Jahre vor | 0

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I am getting this error "Index exceeds the number of array elements. Index must not exceed 1."
You define ICs = 43.4; Therefore, ode15s expects that you want to solve one differential equation. Consequently, "var" in th...

mehr als 2 Jahre vor | 0

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While loop shows the result of the previous run
% Check if there's any change in the matrix positions previous_matrix = matrix; % Store the previous matrix ...

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Run pdepe solver in adjacent domains: introduce flux BC at the interface
If you make r = R_T a point of the r-vector, the finite element solver pdepe will automatically respect continuity of c and dc/d...

mehr als 2 Jahre vor | 0

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Derivative not working plot
clear; clc; close all; % Curve Fit x = [6500 6350 6000 5400 5200 4500]; y = [0 0.25 0.5 0.75 0.875 1.0]; theFit=fit(x'...

mehr als 2 Jahre vor | 0

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while loop running forever during attempt at Newton Rhapson method
Your function doesn't seem to have a zero. d=0.007; dI=1.219; Rfi=1.76*(10^(-4)); Rf0=Rfi; hs=356; ht=hs; kw=60; dTm=29....

mehr als 2 Jahre vor | 0

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For loop doesn't work well.
Somewhere in the line P(i) = P(i-1) - dPD_tot(i); the "dx" must come into play because you usually compute the pressure gradie...

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I have a problem with the convergence of fsolve ?
You could try solution = [10,10,1.2]; % Initial guess for R1, R2, Omega % Solve the equations for eachU value for i = 1:lengt...

mehr als 2 Jahre vor | 1

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How manage for loop to calculate distances?
I should have a new "all_distances" variable with 5 values of distance, but it is only showing the error: Why 5 ? You should ha...

mehr als 2 Jahre vor | 0

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runge kutta algae flower
Don't you have to call rk4 twice for stepsize h/2 to compare the results ? And shouldn't the Runge-Kutta step be pout = xk + (...

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Find all possible combinations of numbers with a specific array length
M = categorical(["A","B","C","D"]); combinations(M,M,M,M,M,M,M,M,M,M,M,M)

mehr als 2 Jahre vor | 1

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Finite method for a heat generating furnace
You use "j" twice as loop index in a nested loop. This will give problems. for j=1:Ny for i=1:Nx if i==Nx...

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Not enough input arguments. Error in mypde_model>bcfun (line 53) ptop =utop - interp1(time, mydata(:,5), t,'spline'); Error in mypde_model (line 17) sol = pdepe(m, @pdefun,
Use sol = pdepe(m, @pdefun, @(z)icfun(z,u_ini1,u_ini2, Z),@(ztop, utop, zbot, ubot,t) bcfun(ztop, utop, zbot, ubot,t,time, myda...

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Unable to find explicit solution.
You must use "dsolve", not "solve": syms t x(t) K eqn = diff(x,t) == (1-x/K)*x; dsolve(eqn)

mehr als 2 Jahre vor | 1

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Doubt in Coupled Ode
Your code is correct, but it seems there is a singularity near 0.32.... syms t x(t) y(t) a1 b1 a2 b2 Constant eqn1 = diff(x,t,...

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Solving a complex system of differential equations
%q(1) = X, q(2) = Y, q(3) = Xdot, q(4) = Ydot M = [1,0.8;0.8,7]; K = [5,0;0,10]; D = [0.15,0;0,0.35]; F = @(t)[5*exp(i*5*t);...

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Piecewise function graph help
L=200; d=10; s=30; r1_max=22.36; r2_max=120.4; r=0:200; for i=1:length(r) if r(i) < d F(i)=0; elseif (r(i) >=d)...

mehr als 2 Jahre vor | 0

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Why are complex values obtained for the below function (x) in the if condition?
Maybe you mean clc close all clear all a = 280; b = 580; c = 0.35; d =1.71E5; e = 7; f = 1+(3.5*(a/b)); g = d/(1+(0.00...

mehr als 2 Jahre vor | 1

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me sale un error en la linea 67: " M(i,j)=buenos(val,3);" y el mensaje es: "Index in position 1 exceeds array bounds (must not exceed 120)"
Add the commands Ni*Nj size(buenos,1) after this line: %% Create output variable buenos = reshape([raw{:}],size(raw)); If ...

mehr als 2 Jahre vor | 0

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Solving PDE and ODE coupled system with varying boundary conditions?
If you want to change a boundary condition, use a second function "fun" and call ode15s with the solution obtained so far and th...

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2 second order differential equations with boundary conditions using bvp4c
Almost the same code as in the preceeding problem: % Parameters alpha = 0.001; gamma = 100; epsilon = 1; delta_v = 0.1; a=...

mehr als 2 Jahre vor | 1

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Fitting two curves with shared parameters to two datasets
clc close all clear all set(0,'defaulttextinterpreter','latex') set(0,'defaultAxesTickLabelInterpreter','latex'); set(0,'de...

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ODE15s Unable to meet integration tolerances without reducing the step size below the smallest value allowed
If you store P for 1:Nx and m for Nx+1:2*Nx, you should also return dPdt for 1:Nx and dmdt for Nx+1:2*Nx. But you return dPdt fo...

mehr als 2 Jahre vor | 1

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Why is my multi-objective optimization with gamultobj (NSGA-II) not working?
Extract your optimization parameters at the time when the integrator returns NaN values. Are they reasonable ? If you think they...

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Interior-point and sequential quadratic programming give me the same answer. Is there an error with my code?
I just saw in your code that you don't pass the options structure to fmincon. Thus in both calls, the same solver is used. Use ...

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