While statement not working

I'm working on a calibration code and for some reason my while statement isn't working. This is what I have:

DT = .002;
L = length(Array);
I=1;
X = .7*f; 
Y = (time-.7)*f;    
FD = Array; 

while I <= L
    A(I) = FD (I);
    I = I +1;     
    DT = DT + .002;
 if DT<=3.5 && DT >= 4
    C = sum (A);      
    Avg_L = C/I;
    I = 2*L;
 end

for some reason my Avg_L is returning as empty. Does anyone know why, if so please help thanks!

[William]

It's much easier for people to help you if your code is formatted correctly. In the upper right part of the questions box click the "Code" button once you've highlighted your code.

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

[Image Analyst]

Looks like it's missing an end statement.

Answer 1

[Image Analyst]

Is this condition ever true:

if DT<=3.5 && DT >= 4

If not, C is undefined unless you previously set it equal to zero. But that would give an error, not a zero. So I guess it must be assigning C, but C=sum(A), which in in turn the sum of FD which is in turn the sum of Array. So is Array all zero?

By the way, do you know how to use the debugger - set breakpoints and examine variables? That is an essential skill that, if you had, could have solved this mystery in a few minutes.