"Index in position 1 exceeds array bounds" error for loop

I'm trying to determine if there is a change in sign between the current and next value in my array (size is 2000 x 131) and count the number of times there is a change using a for loop as shown in the following code. The error lies in line "nextVal = brakingData(j+1,k)". I can't understand why this is an error. Why is the inital value of j 2000 when I run the loop? Shouldn't it be 1? How do I go about solving this error?

for k = 1:size(brakingData,2) %131
    zeroCrossCount = 0;
    for j = 1:length(brakingData) %2000
        currentVal = brakingData(j,k);
        nextVal = brakingData(j+1,k);
        if ~isequal(sign(currentVal), sign(nextVal))
            zeroCrossCount = zeroCrossCount + 1;
        else
             zeroCrossCount = zeroCrossCount + 0;
        end
    end
    brakingFreqValue = zeroCrossCount/20;
    brakingFreq(:,k) = brakingFreqValue;
end

Answer 1

[Rik]

Instead of this line

for j = 1:length(brakingData)

Use this:

for j = 1:(size(brakingData,1)-1)

Although you can replace the loop with an array operation.