perform an action on part of a column in a matrix

Hello

I have a matrix of 3 columns:

The first column contains some numbers that I want to average

Second, either 1 or 0.

3rd is empty because I want to insert values to this column

for example:

5 0 0

4 0 0

6 0 0

4 1 0

7 0 0

8 0 0

9 0 0

7 1 0

1 0 0

4 0 0

3 0 0

What I need is to define a range according to the second column (from the first to the last zero)

calculate the average of the numbers in these rows in column 1

copy the average to column 4

For example:

the average of 5,4,6 is 5

and the average of 4, 7, 8, 9 is 7

so it should look like this:

5 0 5

4 0 5

6 0 5

7 1 7

8 0 7

9 0 7

My questions are:

1. How can I define such range (from zero to zero without 1)?

2. How can I insert the calculated value (the average) into every corresponding row?

Thank you so much for your help!

[Azzi Abdelmalek]

Can you post the correct expected result?

Answer 1

[goerk]

 M %your matrix
 maskData = cumsum(M(:,2));
 for i=0:max(maskData)
   mask = maskData==i;
   meanValue = mean(M(mask,1));
   M(mask,3) = meanValue;
 end

[Tali Leibovich]

Ingenious! Thank you so much goerk!!