Index exceeds the number of array elements. Index must not exceed 0.

clc
close all
R=0.05;                % radius of the bearing 
X=2*pi*R;              % circumference of the bearing
Z=0.1;                  % length of the bearing
M=200;
N=64;                      
delx=1/M;
delz=1/N;
xbar=0:delx:1;
zbar=0:delz:1;
theta=xbar*2*pi;
C=0.0001;                  %clearence
E=0.3;                     %eccentricity ratio  
Ha=0.00009;
nx=6;
nz=6;
const=(R^2)/(Z^2);
fun_hbar = @(theta,z)(1+E*cosd(theta))-((Ha/C)*sind(pi*((theta*nx/2*pi)-1)).^2*sind(pi*(z*nz-1)).^2);
deltheta=theta(end)-theta(end-1); 
h_bar=fun_hbar;
for theta=1:M
    for z=1:N
        H(theta,z)=(1+E*cosd(theta))-((Ha/C)*sind(pi*((theta*nx/2*pi)-1)).^2*sind(pi*(z*nz-1)).^2);
    end
end

fun_hhalf = @(h)(-((h(2)-h(1))/2) + h(2));
fun_hhalf2 = @(h)(((h(2)-h(1))/2) + h(1));
h_halfminus=zeros(size(xbar,2),1);
for i=2: length(h_bar)-1
    h_halfminus(i)=fun_hhalf([h_bar(i-1) h_bar(i)]);
end
h_halfplus=zeros(size(xbar,2),1);
for i=2: length(h_bar)-1
    h_halfplus(i)=fun_hhalf2([h_bar(i) h_bar(i+1)]);
end
h_halfmius=zeros(size(zbar,2),1);
for j=2: length(h_bar)-1
    h_halfminus(j)=fun_hhalf([h_bar(j-1) h_bar(j)]);
end
h_halfplus=zeros(size(zbar,2),1);
for j=2: length(h_bar)-1
    h_halfplus(j)=fun_hhalf2([h_bar(j) h_bar(j+1)]);
end

hm1=h_halfminus(i).^3;
hp1=h_halfplus(i).^3;
hm2=h_halfminus(j).^3;
hp2=h_halfplus(j).^3;
const1=((hp1+hm1)*delz^2+const*deltheta^2*(hp2+hm2));
ITER=1000;
p_bar=zeros(length(xbar),length(zbar));
A1_fun=@(hm1,hp1,hm2,hp2)(hp1*delz^2/const1);
A2_fun=@(hm1,hp1,hm2,hp2)(hm1*delz^2/const1);
A3_fun=@(hm1,hp1,hm2,hp2)(hp2*deltheta^2*const/const1);
A4_fun=@(hm1,hp1,hm2,hp2)(hm2*const*deltheta^2/const1);
A5_fun=@(hm1,hp1,hm2,hp2)(E*sin(theta)*deltheta^2*delz^2/const1);
p_init=p_bar;
error_target = 0.0000001;
h = waitbar(0,'Please wait...');
for k=1:ITER
    for j=2:size(p_bar,2)-1
        for i=2:size(p_bar,2)-1
            p_bar(i,j)=A1_fun(hp1(i),hm1(i),hp2(j),hm2(j))*p_bar(i+1,j)+.....
                       A2_fun(hp1(i),hm1(i),hp2(j),hm2(j))*p_bar(i-1,j)+.....
                       A3_fun(hp1(i),hm1(i),hp2(j),hm2(j))*p_bar(i,j+1)+.....
                       A4_fun(hp1(i),hm1(i),hp2(j),hm2(j))*p_bar(i,j+1)-.....
                       A5_fun(theta(i),hp1(i),hm1(i),hp2(j),hm2(j));
        end
    end
    error = (sum(p_bar(:)) - sum(p_init(:)))/sum(p_bar(:));
    p_init = p_bar;
    if error < error_target
        break;
    end
    waitbar(k / ITER)
end
close(h);

in this at line where p_bar(i,j) starts it gives the error Index exceeds the number of array elements. Index must not exceed 0.

[KSSV]

The variables hm1, hm2, hp2 are empty matrices.....check your code.

[Torsten]

"theta" is used as a loop parameter and overwrote your array "theta".

Thus it is a scalar in the p_bar line, but you address theta(i).

[Walter Roberson]

The error is indexing an empty vector according to the error message, but theta would not be empty as a result of the loop. But hp1 would be empty for the reasons that I described in my answer.

[Torsten]

Ok, then theta(i) would be the next error after repairing hm1,hm2,hp1,hp2.

And unfortunately, many errors follow according to my tests.

Answer 1

[Walter Roberson]

fun_hbar = @(theta,z)(1+E*cosd(theta))-((Ha/C)*sind(pi*((theta*nx/2*pi)-1)).^2*sind(pi*(z*nz-1)).^2);
deltheta=theta(end)-theta(end-1); 
h_bar=fun_hbar;

fun_hbar is an anonymous function. h_bar is assigned a copy of the pointer to the anonymous function.

for i=2: length(h_bar)-1

The length() of an anonymous function is 1, so you are asking for i=2:1-1 which is i=2:0 .

In MATLAB, when the increment is positive and the upper bound is less than the lower bound, the loop control variable is assigned [] (the empty vector); the same is true for negative increment when the upper bound is greater than the lower bound.

    hm1=h_halfminus(i).^3;

i is the last value it was assigned by the for loop; as indicated above, that means that i will be [] because of the bounds issue. So you are indexing some variables at the empty vector, i and getting out empty vectors.