(HELP) Algorithm that notice the moment that a vector with 2 columns varies

Hello guys,

Im very new using matlab and programation.

I have a vector X with 200000 lines and 2 columns, the second column has only 0 and 1 (binary). I would like to make a algorithm that notice me everytime that the second column goes from 0 to 1.

Can someone help?

Thank you

Answer 1

[Joseph Cheng]

you can use the diff() function on the second column. then use the find() function to see which items are 1 (the 0 to 1 transition), 0 (no transition 1 to 1 and 0 to 0, and -1 (1 to 0 transitions).

example:

 transition = diff(X(:,2)); %get the diff of second column for all rows.
 ZeroToOne = find(transition == 1);

the ZeroToOne variable will the the indexes where there is the 0 to 1 transition (located on the 0).

[Joseph Cheng]

 A = [0;1;0;1;1;1;1;0;0;0;1;0]
 Z2O = diff(A);
 trans = find(Z2O==1);

this will result in trans =[1;3;10] and as you can see the answer trans is the location of each 0 to 1 in A.

[Michel]

Thank you, Joseph

Im gonna try

[Michel]

Ok, Joseph.

It shows all the columns that I had the transition == 1.

Now i would like to print the first and the second column in this exaclty moment, because the first column means time and i would like to know the instants that the transition==1 happens. Could you help me? Im reading a sensor sign.

[Michel]

i know how to disp each one like disp(X(1894,:)) for the first transition but im trying a algorithm that show for every transition

[Joseph Cheng]

you can basically do that as well. since you have a list of which rows have the transition ==1 you can go disp(X(transition,:)) which is displaying the variable X for the rows specified in transition, and all columns.

or instead of displaying (which may be thousands of lines) why not store the time? transTimeData = X(transition,:); %save the transition time and data.