Cutting a for loop when a certain value is repeated

Jed
2014 4 16
2 个回答
更新时间：2014 4 16
2 次查看（30 天）

0 个投票

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!

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回答（2 个）

Azzi Abdelmalek
Azzi Abdelmalek 2014-4-16

0 个投票

It's better to use a while loop
while x(k-1)~=x(k)
% your code
end

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Jed
Jed 2014-4-16
编辑：Jed 2014-4-16
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

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Sean de Wolski
Sean de Wolski 2014-4-16

0 个投票

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

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Jed
Jed 2014-4-16
编辑：Jed 2014-4-16
Do you mind explaining what any of that does, sorry. whats ii and nan etc?
Sean de Wolski
Sean de Wolski 2014-4-16
编辑：Sean de Wolski 2014-4-16
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
Jed 2014-4-16
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
Jed 2014-4-16
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

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2014-4-16

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