Question
I get the error '??? Attempted to access corr_up(2e+006); index out of bounds because numel(corr_up)=2000001.' I am looping over a correlated signal looking for threshold cross but continue to get this error. When I attempt to access this element of the array explicitly, 'disp(corr_up(2e+006));` or even 'disp(corr_up(2000000));' , it works without error. Any ideas into this problem. There seems to be enought elements but still getting index out of bounds. i = 1; threshold = max_up/2; while i < length(corr_up) % <--- error thrown here... while corr_up(i) < threshold i = i + 1; end start_of_ping_upsweep = [start_of_ping_upsweep i]; i = i + 0.03*Fs; % look ahead 3 pulse lengths before searching for threshold cross again. end ... ??? Attempted to access corr_up(2e+006); index out of bounds because numel(corr_up)=2000001. Error in ==> check_if_upchirp_or_downchirp_for_90kwqx at 50 while corr_up(i) < threshold
Expert Answer
Prashant Kumar
PhD Expert
Answered Aug 17, 2026
Not true. Inside your while loop you have another while loop
while corr_up(i) < threshold
i = i + 1;
end
with this loop, i could count up basically forever. At some point, i will be more than the length of corr_up.
In general you should NEVER ever use a while loop without a fail safe - a count on the number of iterations. You need to check whether the loop counter is more than the max number of iterations you expect. To fix:
while i <= length(corr_up) && corr_up(i) < threshold
i = i + 1;
if i > length(corr_up)
break;
end
end
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