For loop is not repeating the specified number of times

I am trying to model Butler-Volmer enzyme kinetics in Matlab. Currently, I am trying to produce an array of values for the rates based on a distance d parameter for all of the potentials the model will be at. The direction right now is to use a for loop for the d parameter, but the for loop is not repeating the specified number of times. Instead, a constant value is used for the for loop value (d=12). An array is created when no for loop is used, but then I have run into the problem that matrix dimensions don't match and the k0 * the rest can't be computed. For a description of how I want this to run, for every time point, the values kred and kox should be calculated for every d value.

The code in question (where the constants, a, F, R, T, and Eo are predefined):

v = 0.1;
tfinal = -1.5/v;
tStep = 0.1;
tspan = 0:tStep:tfinal; 
t = tspan;

En = Ei + v * t;

 for d = 4:0.1:12
    
    k0   = 225000 * exp(-d);
    kred = k0 * exp(((-a * F)/(R * T)) * (En - Eo));
    kox  = k0 * exp((((1-a) * F)/(R * T)) * (En - Eo));

 end

And for future reference, I hope the solution can be something that is multipled in a differential equation, such as:

dAdt = -kred*A + kox*B

Answer 1

[SAA]

you can only loop through integers, so you should do something like this:

.....

dt=4:0.1:12;

for d= 4:length(dt)

.....

end