How to iteratively split a matrix into multiple matrices according to a condition?

I have a 2 column matrix with many many rows.

It's been sorted according to the values in the first column.

I now want to split the matrix into ten matrices.

Those values in the first column which are 0-10% of the highest value will go in one matrix, those that are 10-20% of the highest value will go in the next... you get the idea.

How would I go about doing this? I presume a for loop is involved, but am struggling to make it work. Any advice would be very much appreciated - thank you!

Answer 1

[James Tursa]

Assuming values in 1st column are non-negative, you could put the results into a cell array:

M = your matrix
M1 = M(:,1); % 1st column
x = max(M1); % the max value
p = (0:10:100)/100 * x; % the comparison values
p(1) = -1; % Something less than 0 to catch any exact 0 values
result = cell(numel(p)-1,1);
for k=1:numel(p)-1
    result{k} = M( M1>p(k) & M1<=p(k+1) , : );
end

Or if you want to "hide" the loop in the background via arrayfun:

result = arrayfun(@(x,y) M( M1>x & M1<=y , : ),p(1:end-1),p(2:end),'uni',false);

[ishbish]

Amazing, thank you!

Answer 2

[Jan]

M = rand(100, 3);                        % Your data
[~, ~, bin] = histcounts(M(:, 1), 10);   % Split first column into 10 groups
C = splitapply(@(x) {x}, M, bin);        % 10 cells