Help me to set this code?

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Niba Kainat 2023-5-16

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https://ww2.mathworks.cn/matlabcentral/answers/1965204-help-me-to-set-this-code

评论： Torsten 2023-5-16

hi I want to get one specific error value for some specific parameter change. I'm unable to extract specific value of error.

Warning: Unable to meet the tolerance without using more than 2000 mesh points.
The last mesh of 1000 points and the solution are available in the output argument.
The maximum error is 1.62998, while requested accuracy is 0.0001.

function nk

a=0.1;

mu=0.0;

r=2.0;

Ec=0.3;

Nr=10;

solinit= bvpinit(linspace(a,100,1000),[0 0 0 0 0]);

% Set the options with the desired RelTol value

relTol = 1e-4;

AbsTol=1e-6;

options1 = bvpset('RelTol', relTol,'AbsTol',AbsTol);

sol = bvp5c(@Needleode,@Needlebc,solinit,options1);

eta = sol.x; % mesh points

f = sol.y; % solution values at the mesh points

plot(eta,f(1,:))

% Calculate the maximum error

exact_solution=1e-4;

E=max(abs(f - exact_solution));

%disp(E)

% Calculate the number of mesh points

num_meshpoints = length(eta);

%disp(num_meshpoints)

end

function dfdeta = Needleode(eta,f)

Pr=6.8;

Ec=0.3;

mu=0.0;

k=0.0;

Nr=10;

r=3.0;

t1=1+mu*f(4);

t2=1+k*f(4);

u=f(4)*(r-1)+1;

v=eta*(t2+(4/(3*Nr))*(u)^3);

ff1=-(1/(2*eta))*((1/t1)*-2*eta*mu*f(3)*f(5)+t1*f(1)*f(3)+2*f(3));

k_1=f(5)*t2+k*eta*(f(5)^2);

k_2=(1/2)*Pr*f(1)*f(5)+(1/t1)*4*Pr*Ec*f(3)^2;

k_3=(2/(3*Nr))*f(5)*(u^3);

k_4=(4/Nr)*(u^2)*eta*(f(5)^2)*(r-1);

ff2=-(1/(v)*(k_1+k_2+k_3+k_4));

dfdeta=[f(2);f(3);ff1;f(5);ff2];

end

function res = Needlebc(f0,finf)

a=0.1;e=1e-2;

res = [f0(1)-(a*e/2)

f0(2)-e/2

finf(2)-(1-e)/2

f0(4)-1

finf(4)-0

];

end

This is the code .

second i give the the exact solution value myself. How to calculate it manually?

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Torsten 2023-5-16

I don't understand what you try to do and what you are asking for.

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