Grouping repetead values in cells
5 views (last 30 days)
Show older comments
Hi, I would like to group repeated values in a new matrix with four cells. As an simple example lets say that I have these two arrays (a,B) plus a new one (NewE) which is the matrix to my outputs:
a=[1;2;1;2]
NewB=cell(1,length(a))
B=[560800 x 20] %large numerical matrix where the first column contain the same values as in vector "a"
so I think to get the NewB in this simple form whitout using a counter:
for i = 1:length(B)
for j= 1: length(a)
if B(i,1) == a(j,1)
NewB{j}(end+1,:)=B(i,:);
end
end
end
It is obvious that the algoritm doesnt work but the idea was that.
Thank you for your help in advance,
/Fernando
0 Comments
Accepted Answer
Ameer Hamza
on 10 May 2018
Edited: Ameer Hamza
on 10 May 2018
If you want to are trying to separate the rows of matrix B on the basis of values in its column 1, then just use splitapply(),
NewB = splitapply(@(x) {x}, B, findgroups(B(:,1)))
NewB will have the same number of cells as the number of unique elements in B(:,1).
Edit: As stated by @Fernando, that the matrix must be divided into different portions according to the grouping of 1 and 2 in column 1. The following code will work in that case:
index = [0; find(diff(B(:,1))); 20];
portionSize = diff(fliplr(index));
dividedData = mat2cell(B, portionSize, size(B, 2));
you don't need to specify a separate a, the method split the matrix on the basis of consecutive portions in column 1.
0 Comments
More Answers (3)
Jan
on 10 May 2018
% Some test data:
a = [1;2;1;2]
B = rand(560800, 20);
B(:, 1) = randi([1,2], 560800, 1);
% Distribute B over cells of NewB:
NewB = cell(1, length(a))
for k = 1:length(a)
NewB{k} = B(B(:, 1) == a(k), :);
end
While a has repeated values, the resulting NewB contains redundant vectors.
0 Comments
Cathal Cunningham
on 10 May 2018
Is the matrix B in this case a cell array or a matrix? The comment ""%large numerical matrix" would suggest that it's a numeric array but that contradicts "the first column contain the same values as in vector "a" ". For the first column in B to match the vector a it would require that B is a cell array with the first column having a structure such that
B{1,1} = [1;2;1;2]
for the script to consider it a match. The problem statement is a little unclear.
0 Comments
See Also
Categories
Find more on Loops and Conditional Statements in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!