How to split or divide a larger array in to the predetermined size?

My original array is only one dimensional of ordeer 1*15000 and 90% of it consisting zeroes. I want to create smaller arrays where there is non zero values and store them in different array. For example if my original array is [0,0,0,0,6,8,6,0,0,0,0,0,8,8,7,6,87,6,0,0,0] then I want it to split in [6,8,6] and [8,8,7,6,87,6].

I wrote the code to determine the starting and ending position of the non zero element but it is lengthy. Is there any other way?

Answer 1

[Stephen23]

You can use accumarray to put contiguous groups of non-zeros into one cell array:

>> vec = [0,0,0,0,6,8,6,0,0,0,0,0,8,8,7,6,87,6,0,0,0];
>> idx = vec(:)>0;
>> idy = cumsum(diff([0;idx])>0);
>> out = accumarray(idy(idx),vec(idx),[],@(n){n});
>> out{:}
ans =
    6
    8
    6
ans =
    8
    8
    7
    6
   87
    6

[kedar Paul]

@stephen

thank you but i need to store them in an array so that i can operate on them letter, how can i do that? also i was using

sigmask = a>0; signal_start_positions = strfind(sigmask, [0 1]); signal_end_positions = strfind(sigmask, [1 0]);

it was lengthy.

[Stephen23]

@kedar Paul: a cell array is, as its name implies, an array. So the output I gave you is an array already.

If you want to store those values in a numeric array then you need to observe that the number of elements in each group is different, so you can either:

1. Join them together int one vector:

>> vertcat(out{:})
ans =
   6
   8
   6
   8
   8
   7
   6
  87
   6

2. downlaod a FEX submission that concatenates unequal length numeric arrays within a cell array into one numeric array.

Personally I wouldn't bother: keeping the data in a cell array is convenient enough already:

>> out{2}
ans =
   8
   8
   7
   6
  87
   6

[kedar Paul]

@stephen sorry I was not clear, I mean that I want to store the data in matrix form so that I can perform different statistical operation using a for loop. I hope I made myself clear now.

[Stephen23]

It is very simple to loop over the contents of the cell array directly:

for k = 1:numel(out)
    out{k}
end

However if you really want to merge the contents of the cell array back into one numeric array then you will need to use option 2, such as padcat:

 padcat(out{:})