Splitting array based on a single column's condition

Hello, I am trying to separate my large array of [n rows, 5 columns] into individual arrays of [k rows, 5 columns] (where k < n). I want to split my array based on numbers on my fourth column. The fourth column has numbers that increase and decrease in a loop to create some peaks (example: goes from 0 to 35, then from 35 goes to 0, then from 0 to -35, etc.).

I've attached a sample code to help better explain what I mean.

Is there an efficient way to split these data? (So far I've been going into the data selecting where I want to split them up, and doing it manually.)

Thank you in advance.

[Star Strider]

See also: Problem splitting large array into smaller arrays

Answer 1

[Ramnarayan Krishnamurthy]

If the transition point in the fourth column is known to be 0, then you can consider splitting the data by the location of these 0's.

% Locate the zeros in the 4th column  
  index_0 = find(s_P1_5(:,4)==0);
% Include the start and end indices  
  idx = [0 index_0' size(s_P1_5,1)];
% Create individual cells containing the sub matrices
  out = mat2cell(s_P1_5, diff(idx))

The split arrays will now be stored in out{1}, out{2} and so on.

[yz]

This is awesome, thank you! Though, I'm trying to modify your code such that the division happens at the peaks, zeroes, and valleys of column 4. Is there a way to make that new cell output be?:

• cell1: peak to zero
• cell2: zero to valley
• cell3: valley to zero
• cell4: zero to peak
• cell5: peak to zero, etc.

This is what I've done:

 % Locate the zeros in the 4th column  
   index_0 = find(s_P1_30(:,4)==0);

 % Find peaks
   index_1 = find(s_P1_30(:,4)==max(s_P1_5(:,4)));

 % Find valleys 
   index_2 = find(s_P1_30(:,4)==min(s_P1_5(:,4)));

 % Include the start and end indices  
  idx = [0 index_0' index_1' index_2' size(s_P1_5,1)];

 % Create individual cells containing the sub matrices
  out = mat2cell(s_P1_5, diff(idx))

But I'm getting the wrong output. Instead of making the correct cells, I'm taking one huge cells at the end. Is there a way to fix this?

Thank you again!