Index exceeds matrix dimensions error

Hi, I'm running a 105x100 matrix, and it's in line 74 (indicated+attached) that index exceeds matrix dimensions, how can I fix this please?

clear all
format short g

M=100
N=105
tend=5

%Paramters
K=6;
P=0.005
L=201
S=0.2
I=0.3
rw=1
h0=30
c0=3.5
Q=-30

dr=(L-rw)/N
dt=tend/M
D=K/(2*S);
a=D*dt/dr^2
B=D*dt/dr;
y=dt/I*dr;

if dr<2*rw 
    display('dr<=2*rw')
end
while dr>2*rw
    N=input('enter new N')
    dr=(L-rw)/N    
end
if a<=0.5 
    display('a<=0.50')
end
while a>=0.5
    M=input('enter new M')
    dt=tend/M;100
    a=D*dt/dr^2
    if a>=0.5
    display('a not satisfied')
    end
end
A=setupmatrix(N,M);

%Boundary conditions for h 
A(:,1)=h0; %when t=0
A(N,:)=h0; %when r=L
A

for j=1:M 
A(1,j+1)=A(1,j)+2*a*A(2,j)^2-2*a*A(1,j)^2 + (a-(B/2*rw))*(2*dr*Q)/(pi*rw*K)+(P*dt)/S;
end  
A

%index into Matrix h

for j=1:M
    for i=2:N-1
        r=rw+(i-1)*dr ;
        A(i,j+1)=A(i,j)+(a+(B/2*r))*A(i+1,j)^2-2*a*A(i,j)^2+(a-(B/2*r))*A(i-1,j)^2+P*dt/S ;
    end
end
A 

C=setupmatrix(N,M)
d=P*dt+(I-S)*(A(i,j+1)-A(i,j))
for i=1:N
    r=rw+(i-1)*dr ;
    C(i,1)=c0/(1+exp(-((r-180)/4)));
end
 C(N,:)=c0;
 
 for j=1:M
     for i=1:N
           q=(-K/2)*(A(i+1,j)-A(i,j)/dr);            %LINE 74 ERROR
         C(i,j+1)=-y*(q/A(i,j))*C(i+1,j)+(1+y*(q/A(i,j)))-d/I*(A(i,j))*C(i,j)
     end
 end
 
   

FUNCTION setupmatrix :

 function A = setupmatrix(N,M)
A=zeros(1,M)
i=2:N
A(i,:)=zeros
end

[David Hill]

What is setupmatrix() function?

[JaffaCakes]

Oh srry, forgot to include this, It just calculates the matrix for NXM as zeros

function A = setupmatrix(N,M)
A=zeros(1,M)
i=2:N
A(i,:)=zeros
end

[the cyclist]

FYI, your setupmatrix function is completely unnecessary:

A = zeros(N,M);

accomplishes the same thing, much more compactly and efficiently.

[JaffaCakes]

I see I'll try this one out. Thanks a lot :)

Answer 1

[David Hill]

for j=1:M
     for i=1:N%changing to N-1 allows script to run
           q=(-K/2)*(A(i+1,j)-A(i,j)/dr);%A is 105x101 and N=105; therefore, you are indexing A(106,j) on last loop of i (you cannot do that)
         C(i,j+1)=-y*(q/A(i,j))*C(i+1,j)+(1+y*(q/A(i,j)))-d/I*(A(i,j))*C(i,j)
     end
 end

[JaffaCakes]

Amazing makes sense now, Thanks very much :)