MATLAB: Help regarding use of BVP4C in solving an third order ODE.

Question

I'm trying to solve a third order ode using BVP4C and I'm getting this error. Any help ?

Attempted to access y(3); index out of bounds because numel(y)=2.

Error in rhs_bvp (line 2) rhs=[y(2); y(3); y(2)-y(1)*y(3)-1];

Error in bvparguments (line 105) testODE = ode(x1,y1,odeExtras{:});

Error in bvp4c (line 129) [n,npar,nregions,atol,rtol,Nmax,xyVectorized,printstats] = …

Error in Hiemenz (line 4) sol=bvp4c(@rhs_bvp,@bc_bvp,init);

Below is my code

function bc=bc_bvp(yl,yr) %ya(1), ya(2), yb(2)

bc=[yl(1); yl(2); yr(2)-1];

end

function rhs=rhs_bvp(x,y)

rhs=[y(2); y(3); y(2)-y(1)*y(3)-1];

end

init=bvpinit(linspace(0,4,8),[0 0])

sol=bvp4c(@rhs_bvp,@bc_bvp,init);

x=linspace(0,4,8);

BS=deval(sol,x);

plot(BS(:,1),x);

Answer 1

Hi,

this works:

init=bvpinit(linspace(0,4,8),[0 0 0]);
sol=bvp4c(@rhs_bvp,@bc_bvp,init);
plot(sol.x,sol.y(1,:),sol.x,sol.y(2,:),sol.x,sol.y(3,:))
function bc=bc_bvp(yl,yr) %ya(1), ya(2), yb(2)
bc=[yl(1); yl(2); yr(2)-1];
end
function rhs=rhs_bvp(x,y)
rhs=[y(2); y(3); y(2)-y(1)*y(3)-1];
end

Best regards

Stephan