Changing the number of iterations at runtime

I ran MATLAB with 1000 iterations, now it has reached the 500th iteration and I want it to be the last iteration. Is this possible while running the code?

Answer 1

[Walter Roberson]

I suspect you are talking about for loops.

The answer for those is that that cannot be done.

You can modify the loop index, but as soon as the next iteration starts, MATLAB will overwrite with the next value of the variable. The current iteration value is effectively held in a hidden variable, so changes to the loop control variable do not affect the looping.

You can put in a breakpoint, but once stopped, you cannot use "break" or "continue" or "return". You can dbquit but if you do then execution will stop without executing any further lines of code.

If you have a situation where you expect that you might want to break early, then you should code in the possibility, such as

break_early = false;
for K = 1 : 1000
    stuff here
    if break_early; break; end
end

Then if you breakpoint in the loop, you can set the variable break_early to true and the loop will terminate the next time the test is reached.

[Walter Roberson]

Another approach to consider is to use a try/catch and generate an error at the breakpoint. Something like

try
    for K = 1 : 1000
        stuff here
    end 
catch ME
   %user stopped early
end
stuff after loop