MATLAB: Identifying the elements of a cell

cell arrays

I have a 700×8 cell, with each cell having a matrix 6×2 in size. I want to get the first row of each cell. How do I perform this?

Best Answer

From my understanding of the question, you can achieve the required task by following snippet of code:

cnt = 1;
for i = 1:700
  for j = 1:8
    a(cnt) = C{i,j}(1,:);  % stores the first row of each cell in a;
    cnt = cnt + 1;
  end
end

Related Solutions

MATLAB: Accessing an element of an array using an array as its index.

Interesting...I guess your question title should be edited to "use array as subscripts into multidimensional array". I dug into the sub2ind() to extract how to use subscripts to get a linear index and came up with this test

siz = [4,3,5,7]
subs = [1,2,4,6]
subsc = num2cell(subs)
ndx = sub2ind(siz,1,2,4,6)
ndx = sub2ind(siz,subsc{:})
ndx = subs(1);
k = cumprod(siz);
for i = 2:length(subs)
	ndx = ndx + (subs(i)-1)*k(i-1);
end
ndx

So you should be able to do

function ndx = sub2ind_a(siz,subs)
% no-check version of sub2ind, with input array of subs
ndx = subs(:,1);
k = cumprod(siz);
for i = 2:size(subs,2)
	ndx = ndx + (subs(:,i)-1)*k(i-1);
end
end

And in your code:

siz = size(DATA); % somewhere at the top
% and in your loop
a(cnt) = DATA(sub2ind_a(siz,idx));

For readability I would change your variable name "idx" to "subs_a" or something.

MATLAB: How to concatenate each element of a cell array across rows

for i=1:size(a,1)
    a(i)={horzcat(a{i,:})};
    a{i,1}=reshape(a{i,1},2080,1);
end
a(:,2:size(a,2))=[];

Best Answer

Related Solutions

MATLAB: Accessing an element of an array using an array as its index.

MATLAB: How to concatenate each element of a cell array across rows

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