Nested While and For Loop

Have the following code with an error stating "Array indices must be positive integers or logical values." Could someone point me in the direction of what this error means or why i'm getting it. It occurring in the second while and i'm assuming will happen again in the third

Eqn1 = @(x) 5*(1-erf(3*x));
Eqn2 = 0;
Eqn3 = @(x) 5*(1-erf(3*(x-30)));
X0 = 0;
X1 = 1;
X29 = 29;
X30 = 30;
Int1 = 10;
Int2 = 100;
Value1 = ((X1-X0)/Int1);
Value2 = ((X29-X1)/Int2);
AreaReq5 = 0;

while (X0 < X1)
    AreaReq5 = AreaReq5+(Value1/2)*(Eqn1(X0)+Eqn1(X0+Value1));
    X0 = X0+Value1;
    while (X1 < X29)
    AreaReq5 = AreaReq5+(Value2/2)*(Eqn2(X1)+Eqn2(X1+Value2));
    X1 = X1+h5b;
    end
    while (X29 < X30)
           AreaReq5 = AreaReq5+(Value1/2)*(Eqn3(X29)+Eqn3(X29+Value1));
    XNow = X29+Value1;
    end
end

Answer 1

[Torsten]

Eqn2 = @(x)zeros(size(x));

Answer 2

[Stephen23]

You define Eqn2 to be zero:

Eqn2 = 0;

and then inside the loop you try to access it using indexing:

Eqn2(X1+Value2)

When the error occurs the value of that index is:

>> X1+Value2
ans =  1.2800

Clearly this is not an integer.