# Repeating or rerunning a loop

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Olivia Krieger on 1 Apr 2019
Edited: Olivia Krieger on 2 Apr 2019
Hello MATLAB community! I am hopeful that someone can help me solve this puzzle I've created for myself...
I am running an experiment using an eye tracker. When an eye movement is detected, I want to record the trial sequence number and then add those trials onto the end of the trial block. But once I'm through the loop I don't know how to restart the loop with a new sequence/new number of iterations.
This is an example of my loop (the real loop is quite long and complex)
seq = [3, 1, 2, 1, 3, 2]; % trial sequence
nTrials = length(seq);
addTrials = [];
for trial = 1:nTrials
option = seq(trial);
if option == 1
% do this
elseif option == 2
% do that
elseif option == 3
% do another thing
end
movement = 0;
% check for eye movements
if eye movement is detected % this is not real code
movement = movement + 1
end
% add trial with movement to new sequence vector
if movement > 0
addTrials = [addTrials option];
end
end
% Question: how can I get the loop to rerun using
% nTrials = length(addTrials) and option = addTrials(trial)
I am also open to other ways to solve this than I've currently started!
Thanks!
##### 2 CommentsShowHide 1 older comment
Olivia Krieger on 2 Apr 2019
Hi, I check for eye movements in various places within the trial loop, so I've just added (from your suggestion)
if movement > 0
seq(end + 1) = option;
end
Thank you!!

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### Accepted Answer

Jos (10584) on 1 Apr 2019
Use a while loop, which is more flexible than a for -loop. Something like this might work:
seq = [3, 1, 2, 1, 3, 2]; % trial sequence
k = 0 ;
while k < length(seq),
k = k + 1 ;
option = seq(k);
% check for eye movements
if eye movement is detected % this is not real code
% add trial with movement to the sequence vector
seq(end+1) = option ;
end
end
##### 1 CommentShowHide None
Olivia Krieger on 2 Apr 2019
Edited: Olivia Krieger on 2 Apr 2019
Thank you!! This is very helpful and should work to resolve my issue, it worked in a little psuedocode I made. I will implement today in the actual experiment!

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