how to break the loop

Question

Busy Bee 2018-1-11

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评论： Busy Bee 2018-1-11

I have a matrix p;

now, i only need points until they are increasing. Once the value decreases i need to break the loop and end the process. here i have tried to use the loop,

for i=1:length(p)
if p(i,1)<p(i+1,1)
one(i,:)=p(i+1,:)
else h=p(i,:)
end
end

but it only gives the result till 0.9102. I also want to include the value 0.9528 and then break the loop.(i need to break the loop here because my matrix is nearly 100*2 and this condition might be true in the next rows). What am i doing wrong?

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Guillaume 2018-1-11

The code you've shown is guaranteed to result in an index exceeds matrix dimension error, so it's unlikely that it only gives the result till 0.9102 since it will error before completion.

Busy Bee 2018-1-11

I have 100*2 matrix. I am using the code only for the first column.

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Answer 1

Guillaume 2018-1-11

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What am i doing wrong?

Using length with a matrix ( length can be the number of rows or columns)
Indexing past the end of the matrix. When i is the index of the last row p(i+1, 1) is not valid. This will result in and index exceeds matrix dimension error
Growing the one array inside the loop
Using a loop

To break out of a loop, you use break.

for i = 1:size(p, 1)  %do not use length on matrices!
  if somecondition
      dosomething
  else
      break;  %quit the loop
  end
end

But the loop is a complete waste of time:

idxstop = find(diff(p(:, 1)) < 0, 1);  %find index of first value where the difference is negative
one = p(1:idxstop, :)  %and extract all rows up to that index