index exceeds matrix dimensions

%consolidation for PTPB

H=10; % total depth of section

Cv=0.5; %in m^2/day

U0=100; %initial U

U1s=0;

U2s=0;

dz=1; % depth of interval

n=H/dz; %no. of depth intervals

t=40; %time in days

dt=1; %time interval

m=t/dt; %total no. of time intervals

Yw=9.81; %in KN/m2

U=zeros(n,m);

i1=input('give value of thresold gradient');

i1=fprintf('i1= %d \n',i1);

a=input('give value of a= %d');

a=fprintf('a= %4d \n',a);

alpha=input('Enter value of alpha= %5d');

alpha= fprintf('alpha = %d \n',alpha);

M=zeros(n,m);

j=0;

for l=dt:dt:39*dt

j=j+1;

for i=2:n

M(i,j)=1-(1-a)*alpha*(1-exp((-alpha/(i1*Yw)*(U(i+1,j)-U(i-1,j))/(2*dz))));

end

end