How to use a for-loop to find the onset (first element) of trials of zeros, ones and twos, in an array of sequences of zeros, ones and twos

I am trying to make a function that finds the onsets (three different) trials (in this case, the trial starts when a new sequence of zeros, ones and twos starts in an array of numbers, this array of numbers always consists of sequences of ones, zeros and twos).

See the example of such an array (E) for a clarification:

E = [zeros(1,10) ones(1,5) zeros(1,8) 2*ones(1,4) zeros(1,12)] 

This array is always a rowvector. The example consists of 5 trials, and 39 elements (10+5+8+4+12).

With the funtion, I want to find the elements (1:39) of the starts of every trial: [start_of_trial], with the corresponding value 0, 1 or 2: [trial_value]. This way, the function will be as follows:

 [start_of_trial, trial_value] = find_onsets(E)

How can I use a for-loop to make this function work? I tried several things, but nothing worked properly

Answer 1

[Andrei Bobrov]

function [start_of_trial, trial_value] = find_onsets(E)
    start_of_trial = find([1;diff(E(:))~= 0]);
    trial_value = E(start_of_trial);
end

[Sterre]

The function works, thank you.

Although it is not necessary here, I need to have a for-loop in the function.. Can you help me with that?

Answer 2

[Catalytic]

No, we're not going to do your homework for you. Go away and leave us alone.