why do i receive this error please help to rectify the error.

the boundary conditions are

a'(0)=0 a(1)=1

b(0)=0 b(1)=0

function steady
m = 0;
x = linspace(0,1);
t = linspace(0,10000);
sol = pdepe(m,@pdex4pde,@pdex4ic,@pdex4bc,x,t);
u1 = sol(:,:,1);
u2= sol(:,:,2);
%figure
plot(x, u2(end,:),'m')
hold on
%title('u1(x, t)')
%xlabel('Distance x')
%ylabel('u1(x,t)')
%figure
% --------------------------------------------------------------
function [c,f,s] = pdex4pde(~,~,u,DuDx)
phi=0.001;ks=1;kp=1;al=0.1; %These parameter values are used in Fig.2
c = [1;1];
f = [1;1].* DuDx;
F1=phi.^2.*u(1)./(1+(u(2)./kp)+u(1).*(1+(u(1)./ks)));
F2=-al.*phi.^2.*u(1)./(1+(u(2)./kp)+u(1).*(1+(u(1)./ks)));
s = [F1;F2];
% --------------------------------------------------------------
function u0 = pdex4ic(~)
u0 = [1; 1];
% --------------------------------------------------------------
function [pl,ql,pr,qr] = pdex4bc(~,~,ul,ur,~)
pl = [0;ul(2)];
ql = [1;0];
pr = [ur(1)-1;ur(2)];
qr = [0;0];
%qr = [0; bi*(1-ur(2))];

Error

Index exceeds the number of array elements (1).

Error in steady>pdex4bc (line 28)

pl = [0;ul(2)];

Error in pdepe (line 250)

[pL,qL,pR,qR] = feval(bc,xmesh(1),y0(:,1),xmesh(nx),y0(:,nx),t(1),varargin{:});

Error in steady (line 5)

sol = pdepe(m,@pdex4pde,@pdex4ic,@pdex4bc,x,t);

Answer 1

[Walter Roberson]

function [pl,ql,pr,qr] = pdex4bc(~,~,ul,ur,~)

ul is passed as the second parameter to pdex4bc, not the third entry.

[Mallikarjuna M]

Thank you it worked