How can I use elements of a vector for the '' for loop '' ?

I want to code some simple formulas for the ultimate strength calculation of ship panels. I have coded nested for loop in a function. Inner loop uses elements of a vector as loop boundary. But in this case, it gives some incorrect results. Related part of my code is attached. In my code N is a vector whose dimension is kx1. I have to use every single element of N vector as boundary for inner loop. Other vectors have been calculated previously.

Thank you so much in advance.

Best Regards.

Murat

[Geoff Hayes]

In your attached code you show

for j=1:N(i)  %%%%%problem is here %%%%%
  yi(j)=j*b(i);
  Lcr2(j)=sin(pi*yi(j)/Btotal(i))^2;
  Lcr3(j)=cos(pi*yi(j)/Btotal(i))^2;
end

You've stated that N is a kx1 vector and that inner for loop...gives some incorrect results. What are those incorrect results? Are you observing an error, and if so what is it? Are the values of j as it iterates from 1 through to the N(i) value valid for your yi, Lcr2 and Lcr3 vectors?

[ITU]

Dear Mr. Hayes

I have FEM eigenvalue results for the stiffened panels. I can compare the results of FEM and simplifed formulas and it can be easily observed that results are different. N vector contains the number of stiffeners for each panel(288 panels). For instance, when I use 2 instead of N(i), it gives consistent results with FEM for the case of two stiffened panels. However, when I want to read from N vector, the code does not read the correct value from the vector. Finally, the answer for your last question is yes. values of j are valid for yi, Lcr2, Lcr3 vector.

With Best Regards

Murat

[Geoff Hayes]

What are the typical values of N? What makes you think that the code is not reading the correct value from the vector? If i is two, then what is N(2)? Try stepping through the code with the debugger to see what N(i) is for the first couple iterations of i.

See Per's answer below and in particular his test. Your code would behave in a similar fashion. Is the output (in his answer) not what you would expect?

[ITU]

Typical values of N are 1,2,4,8. i is not just 2. i represents the panel number which is from 1 to 288. For instance, N(1)=1, N(2)=2, N(3)=4, etc. But the attached code does not read the intended value.

[ITU]

I think there is a problem with Per's answer, so I couldn't see that.

[Geoff Hayes]

So what value does the code read if not the intended N(i)? Please add the following line of code as the first line in the inner for loop

 fprintf('N(i)=%d i=%d j=%d\n',N(i),i,j);

Just have the code run for the first handful of i (maybe 1 through to 5 or so) and observe the output of the above fprintf. Paste it back here and indicate what the code should read versus what it is reading.

[ITU]

Dear Hayes,

The problem has been solved, the problem is not about N(i) but about dimensions of yi(j), Lcr2(j) and Lcr3(j). N(i) > N(i+1) is some cases, so new iteration writes the new vector over the previos one. Finally, summation of elements of these vector gives undesired values. Thank you so much for your nice support.

Best Regards.

Murat