Help with simple probability calculation (loop?)

I have a 2-column matrix that looks like this:

30     1
30     1
30     1
30     1
30     1
29     0
29     1
29     1
28     1
28     1
28     0
28     0

"1" indicates an occurrence and "0" does not. I need to compute a probability for each unique number in column 1. So the answers should be:

30 = 1
29 = .6667
28 = .50

Now, I have the "count_unique" function from the file exchange that counts the unique numbers and identifies how many occurrences there are for each number. Using this, I have tried to write a for loop that computes this problem, but I am stuck in the mud. I'm grateful for any assistance. Happy Thanksgiving.

Answer 1

[Star Strider]

I don’t know how robust this is, but it works here:

M = [30     1
    30     1
    30     1
    30     1
    30     1
    29     0
    29     1
    29     1
    28     1
    28     1
    28     0
    28     0];

raw_freq = accumarray(M(:,1), 1);
adj_freq = accumarray(M(M(:,2)>0), 1);
Prob = adj_freq./raw_freq;
Mu = unique(M(:,1));
Result = flipud([Mu Prob(~isnan(Prob))])

Result =
           30            1
           29      0.66667
           28          0.5

[Cary]

Thanks as always Star! Happy Holidays.

[Star Strider]

And as always, my pleasure!

You, too!