Get the numbers of rows where values change

Hi,

I have an array of data, structured like this:

Latitude Longitude Height

23 54 7

23 54 3

23 54 8

23 55 4

23 55 2

24 54 0

24 54 1

24 55 2

24 55 7

How can I get the numbers of the rows where either Latitude or Longitude changes (so from the example above the output would be rows 3, 5 and 7)?

[Image Analyst]

By the time you get down to row 3, nothing has changed yet. Row 3 is still the same as rows 1 and 2. Don't you mean 4, 6, and 8? Those are the actual rows where a change is first encountered.

[Maja Zdulska]

Yes, sorry, you're absolutely correct.

Answer 1

[Image Analyst]

By the time you get down to row 3, nothing has changed yet. Row 3 is still the same as rows 1 and 2. Don't you mean 4, 6, and 8? Those are the actual rows where a change is first encountered.

Try this:

m = [
	23	54    7
	23	54    3
	23	54    8
	23	55    4
	23	55    2
	24      54    0
	24	54    1
	24	55    2
	24	55    7]
latChanged = [0; diff(m(:, 1))] % Logical -- use find() if you want row numbers.
lonChanged = [0; diff(m(:, 2))] % Logical -- use find() if you want row numbers.
eitherChanged = find(latChanged | lonChanged) % Row numbers where either lat OR lon changed.

[Maja Zdulska]

Many thanks.

Answer 2

[David Hill]

b=diff(a);%a being your matrix
c=find(b(:,1)~=0|b(:,2)~=0);%c=3,5,7