# Ignoring when indexing value positions are invalid

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Morten Jørgensen on 1 Apr 2019
Answered: Jan on 1 Apr 2019
Hi
I get and error when running this code, is it possible to ignore when position is invalid at just let the code proceed?
so it stille includes as many as possible?
thanks
for o = 1:length(mBall)
if mBall(o,4:5) == 0
mBall(o,6) = 1;
elseif sum(displace(o-25:o+25,1)) < 2
mBall(o,6) = 3;
else
mBall(o,6) = 0;
end
end
%Index in position 1 is invalid. Array indices must be positive integers or logical values.
%Error in Velocity (line 93)
%elseif sum(displace(o-25:o+25,1)) < 2
##### 2 CommentsShowHide 1 older comment
Morten Jørgensen on 1 Apr 2019
yes I know, but I'm asking if it is possible to ignore this error
so when o = 24, it will only take the 24 first indces into account? instead of evaluating when the negative as well

Image Analyst on 1 Apr 2019
Try this
for k = 1 : length(mBall)
if all(mBall(k,4:5) == 0)
mBall(k,6) = 1;
elseif k >= 26
if sum(displace(k-25 : k+25,1)) < 2
mBall(k,6) = 3;
else
mBall(k, 6) = 0;
end
else
mBall(k,6) = 0;
end
end

Jan on 1 Apr 2019
"when o = 24, it will only take the 24 first indces into account"
for k = 1:length(mBall)
if mBall(k, 4:5) == 0
mBall(k, 6) = 1;
elseif sum(displace(max(1, k-25):k+25,1)) < 2
mBall(k, 6) = 3;
else
mBall(k, 6) = 0;
end
end
"o" can be confused with "O" or "0", so "k" is used here instead.
You should not "ignore" an error, but create some code to avoid it. Here the index cannot be smaller than 1, so set 1 as minimal index explicitly. Or maybe:
elseif k > 25 && sum(displace(k-25:k+25,1)) < 2