For loop indexing error

ri = 40.34;
rf = 40;
Em = 3.5e-9;
Ef = 1000e-9;
z = linspace(0,0.34,12);
n=1;
E = zeros(12);
r = zeros(12);
for j = 1:12
    r(j)= z(j)+40;
    E(j) = Em*(ri/r(j))+(((ri-r(j))/(ri-rf))^(n/2))*(Ef-Em(ri/rf));
end

I'm getting this error

Array indices must be positive

integers or logical values.

Error in interface_modulus

(line 11)

E(j) =

Em*(ri/r(j))+(((ri-r(j))/(ri-rf))^(n/2))*(Ef-Em(ri/rf));

Answer 1

[KSSV]

ri = 40.34;
rf = 40;
Em = 3.5e-9;
Ef = 1000e-9;
z = linspace(0,0.34,12);
n=1;
E = zeros(12);
r = zeros(12);
for j = 1:12
    r(j)= z(j)+40;
    E(j) = Em*(ri/r(j))+(((ri-r(j))/(ri-rf))^(n/2))*(Ef-Em*(ri/rf));
end

Type error:

Replaced

Em(ri/rf)

with

Em*(ri/rf) 

When you try Em(ri/rf), it will take as index..and the value comes to be fraction. The indices cannot be fraction..so error.