bvp4c: a singular Jacobian encountered

Hi everybody! I'm trying to solve the following second order differential equation with known boundary conditions:

 global a0 a1 a2 a3 a4 h k JA JB
  % J/m^2 -> N/m
 a0 = 2.0377638272727268;
 a1 = -7.105521894545453;
 a2 = 9.234000147272726;
 a3 = -5.302489919999999;
 a4 = 1.1362478399999998;
  k = 5.92*10^-3;   % N/m
  h = 45.5 *10^-10; % Angstrom -> m

JA = 1.025;
JB = 1.308;
XA = 0;
XB = 45;

meshX = linspace(0,45,100);
Y0 = [JA, JB]; %guess values
init = bvpinit(meshX,Y0);
sol = bvp4c(@myode,@mybc,init);

==============

function yprime = myode(x,y)
global a1 a2 a3 a4 h k

H = h^2/12;
B = a1 + 2*a2.*y(1) + 3*a3.*y(1).^2 + 4*a4.*y(1).^3;
C = 5*a1 + 8*a2.*y(1) + 9*a3.*y(1).^2 + 8*a4.*y(1).^3;

yprime = [y(2);
         (C.* y(2).^2)./(B.*y(1)) + (y(1).^5)./H - (k.*y(1).^5)./(H.*B)];

================

 function res = mybc(ya,yb)
 global JA JB

 res = [ya(1) - JA
        yb(1) - JB];

The function J(x) assumes the values JA and JB at the extremes of the interval. As reported in the title, I get the following error:

"Error using bvp4c (line 252) Unable to solve the collocation equations -- a singular Jacobian encountered.

Error in mybvp (line 54) sol = bvp4c(@myode,@mybc,init);"

How can I overtake this problem? Thanks in advance for your help. Pinco

[Pinco]

any ideas?

[Kye Taylor]

You bump your questions in hopes that they will be answered. Another good way to encourage answers is to accept good ones to previous threads.

[Pinco]

@Kye Taylor: I apologize for this, but I know that you accept when the problem is solved, or is it not right? If the latter is the case, I apologize again, I will accept also the useful answers. Could you also explain to me the use of the flag? I'm not very familiar with this forum.

I posted a new question because it became different from the previous one.

Thanks for your help, but I studied the Jacobian and overtook this problem.

[Kiran Pathapati]

@Pinco,

I'm also facing the same errors that you have mentioned in your earlier message. "Error using bvp4c (line 252) Unable to solve the collocation equations -- a singular Jacobian encountered.

Error in mybvp (line 54) sol = bvp4c(@myode,@mybc,init);"

You have mentioned that you were able to fix the errors. Could you please help me fixing the issue.

Thanks, Kiran

Answer 1

[Sri Mukessh Subramanian]

the boundary condition vector should be specified column wise NOT ROW wise