error with Bvp4c - Unable to solve the collocation equations -- a singular Jacobian encountered.

I am trying to solve a second order boundary value problem using bvp4c

d^2y1/dz^2 = .2*y1

d^2y2/dz^2 = .2851*y1

y1(z=0) = .21

dy2/dz(z=0) = 0

y2(z=1) = 0

dy1/dz(z=1)=.127

my functions are

function dydz = bvpfcn(z,y) % equation to solve
dydz=[y(2)
.2*y(1)
y(4)
.2851*y(1)];
end

function res = bcfcn(ya,yb) % boundary conditions
res = [ya(1)-.21
       0
       yb(2)-.127
       0];
end

function g = guess(z) % initial guess for y and y'
g = [-.001*z
    -z
     .001*z
     z];
end

mesh = linspace(0,1);
solinit = bvpinit(mesh, @guess);
sol = bvp4c(@bvpfcn, @bcfcn, solinit)

Is this becuase both of my functions depend on y1?

Thank you

Answer 1

[darova]

Your boundary conditions are wrong. Try these

function res = bcfcn(ya,yb) % boundary conditions
res = [ya(1)-.21    %  y1(z=0) = 0.21
       ya(4)-0      % dy2(z=0) = 0
       yb(3)-.127   %  y2(z=1) = 0.127
       yb(2)-0];    % dy1(z=1) = 0