Ignoring when indexing value positions are invalid

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

[KSSV]

If o is < 25, you will get indices negative.......so the error.

[Morten Jørgensen]

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

Answer 1

[Image Analyst]

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

Answer 2

[Jan]

"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