How can I fix "Index exceeds the number of array elements (1)."

This is my script.

function [ca, depth] = transientDiffModel(B,Ds,H,ct,dz,t,th)
B= input(' B:degradation rate of antibiotic in biofilm, in s^-1: ');
Ds= input('Ds:diffusion constant of antibiotic, in mm^2/s:');
H= input('H: total depth of biofilm, in mm:');
ct= input('ct: strength of source of antibiotic at z=0, in ug*mm/L:');
dz= input('dz: step size in depth for simulation, in mm:');
t= input('t: time at which concentration profile is being computed, in s:');
th= input('th: threshold below which a concentration is considered to be zero, in ug/L:'); 

n=1;
z(1)=0;
ca(1)=ct/sqrt(4*pi*Ds*t)*exp(-B*t);
while ca(n)>=th || z(n)<H;
        n=n+1;
        z(n)=z(n)+dz;
        ca(n)=ct/sqrt(4*pi*Ds*t)*exp(-z(n)^2/(4*Ds*t)-B*t);
end
end

When I run the code, it says:

Index exceeds the number of array elements (1).

Error in transientDiffModel (line 33)

z(n)=z(n)+dz;

Answer 1

[KSSV]

Modify it to:

function [ca, depth] = transientDiffModel(B,Ds,H,ct,dz,t,th)
B= input(' B:degradation rate of antibiotic in biofilm, in s^-1: ');
Ds= input('Ds:diffusion constant of antibiotic, in mm^2/s:');
H= input('H: total depth of biofilm, in mm:');
ct= input('ct: strength of source of antibiotic at z=0, in ug*mm/L:');
dz= input('dz: step size in depth for simulation, in mm:');
t= input('t: time at which concentration profile is being computed, in s:');
th= input('th: threshold below which a concentration is considered to be zero, in ug/L:'); 

n=1;
z(1)=0;
ca(1)=ct/sqrt(4*pi*Ds*t)*exp(-B*t);
while ca(n)>=th || z(n-1)<H;
        n=n+1;
        z(n)=z(n-1)+dz;
        ca(n)=ct/sqrt(4*pi*Ds*t)*exp(-z(n-1)^2/(4*Ds*t)-B*t);  % decide here z(n) or z(n-1)
end
end

[Aimee Jin]

thank you!