Cutting a for loop when a certain value is repeated

Is there any way of cutting a for loop when a certain value is reached? I have a loop in the form of

for k = 1:numel(filelist)

this loop produces a value of X at the end of every loop which is then stored in a text file. I was just wondering whether there is any way that the for loop can be cut when this value of X stops increasing/ stays the same?

I thought something maybe along the lines of

if X(k-1)==X(k)
    break
end

but this doesn't work. I guess its because the loop overwrites X. I was just wondering whether anyone had any ideas? Thanks in advance!

Answer 1

[Azzi Abdelmalek]

It's better to use a while loop

while x(k-1)~=x(k)
  % your code
end

[Jed]

sorry i forgot to mention that there are multiple 0 values at the very beginning. It is for a spray injection where there are multiple images showing zero spray, spray then starts and then i wanted it to cut-off when it stops increasing. And also how does that work when x hasn't been defined yet? as it is defined at the end of the loop

Answer 2

[Sean de Wolski]

Sure, pseudocode:

xtemp = nan;
for ii = 1:1000
 x = whatever
 do stuff
 if x==xtemp
     break
 else
    xtemp = x;
 end
end

[Jed]

Do you mind explaining what any of that does, sorry. whats ii and nan etc?

[Sean de Wolski]

ii is just the for loop iterator. I set xtemp to nan because nothing equals nan. This means the first iteration will run through no matter what and the second is the first that can fail. After that, on each iteration, we test if the new x is equal to the old one, if it is, break, if it isn't don't break and store the new current value for x in xtemp for the next iteration.

[Jed]

Aw thank you! that makes much more sense now. In this case though there are either 4 of 5 blank images at the beginning where x=0 which would break this loop too early. Is there any way to get around this?

[Jed]

i tried putting that within its own while loop, saying:

while X>0
 if X==Xtemp
     break
 else
    Xtemp = X;
 end
end

but that didnt work, it completely ignored the whole statement