global variable in for loop

Hi,

I have a for loop, which has last iterative defined as the size of some matrix K, i.e.

[a,b]=size(K)

for i=1:a

CODE

end

Trouble is, the "CODE" in the for loop redefines how large K is - in particular, it decreases a. This means that the for loop experiences an "Index exceeds matrix dimensions." error. How does one go about fixing this? I thought that in the for loop I could have:

a=a-1;

everytime the "CODE" decreases the size of K, but it don't work none!

Thanks,

Linford

Answer 1

[Walter Roberson]

If you are deleting the entry you are examining under some circumstances, then the easiest change is often to run the loop backwards .

Answer 2

[Jan]

The argument of the FOR loop is calculated once and is not influenced by the contents of the loop - in opposite to C.

You can check the exceeding index explicitely:

[a,b] = size(K);
for i = 1:a
  if i > size(K, 1)
    break;
  end
  CODE
end

Using a WHILE loop is a nice alternative:

[a,b] = size(K);
while i <= size(K, 1)
  CODE
  i = i + 1;
end