How can I recover data stored in cells ?

Hello, I have been doing some work in Matlab and I am unfamiliar with using cells. I would like to know how to access data which I have stored in cells. I have tried cell2mat(), but I get the following error:

Error using cell2mat (line 52) CELL2MAT does not support cell arrays containing cell arrays or objects.

if true
% cx = centerxFinal;
% cy = centeryFinal;
% rad = radiusFinal;
% 
% columns = size(centeryFinal,2);
% rows = size(centeryFinal,1);
% 
% for i = 1:columns-1
%     for j = 1:rows
%         for k = 1:rows
%             if ((cy(j,i+1) ~= 0 && cy(k,i) ~= 0) && (cx(j,i+1) ~= 0 && cx(k,i) ~= 0))
%                 y_dist(j,i,k) = cy(j,i+1)-cy(k,i);
%                 xy_points{j,i,k} = {[centeryFinal(j,i+1),centeryFinal(k,i)],[centerxFinal(j,i+1),centerxFinal(k,i)]};
%                 x_dist(j,i,k) = cx(j,i+1)-cx(k,i);
%             else
%                 xy_points{j,i,k} = 0;
%             end
%         end
%     end
%  end           
% for i = 1:columns-1
%     for j = 1:rows
%         for k = 1:size(xy_points,3)
%             if y_dist(j,i,k) > 50 || y_dist(j,i,k) < -50
%                 xy_points{j,i,k} =0;
%             end
%             if x_dist(j,i,k) <= 0 || x_dist(j,i,k) < 400
%                 xy_points{j,i,k} =0;
%             end
%         end
%     end
% end  
end

The result of this script is a three dimensional cell containing cells which cointain pairs of points.

Is there a function or algorithmic process I can use to retrieve the data points that have survived the filtering process?

Answer 1

[Image Analyst]

To recover data stored in cells, you also use the braces again:

cellContents = xy_points{j,i,k};

I see no reason in your code to mess with cells at all. You don't have stuff of variable type or size. To make it even more confusing, it seems like the variable editor is saying you have cells inside of cells. How confusing is that?

See the FAQ for a good intuitive discussion of what cells are: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F

[Constantine Papakonstantinou]

Hi and thanks for answering,

I have a matrix containing information and I wanted to compare every row for a specific column with every row in the adjacent column to retrieve information on how the quantities relate to each other e.g. distance along the x-axis, or y-axis. and then filter the data for specific conditions. In order to collect the information I assumed I could store the data points I was comparing as an array {[x(row, column) x(row, column+1)], [y(row, column),y(row,column+1)]}. So for a corresponding index combination (I,j,k) of my collected distance information y_distance(I,j,k) I can retrieve the corresponding compared points which resulted in the information for that index combination inside of the cell.

for example if

cell{I,j,k} = {[x1,x2],[y1,y2]} for some I,j,k

I want to be able to access [x1,x2] and [y1,y2]

I'm not concerned with storing different data types, as I am with storing combinations of data points. I thought using a cell would let me store arrays which contain combinations of data points.

are you suggesting there is a better way to do this without using a cell ?

[Image Analyst]

I don't understand. For a location of (row, column), the distances to the other pixels in the next column is simply going to be sqrt(1), sqrt(2), sqrt(3), sqrt(4), etc. In general:

totalRows = 10
thisRow = 4;
% Find distance of element in thisRow to element in next column for all rows.
deltaY = -(thisRow - 1) : (totalRows - thisRow)
deltaX = 1; % It's just the next column over.
distances = sqrt(deltaX.^2 + deltaY.^2)

[Constantine Papakonstantinou]

I was using the code above to organize the output data of a different portion of script. The centroids of some objects which moved across a sample space in a sequence of images. The resulting data that I'm working with represent centroids in a specific frame where the column index is representing the frame number. In this case I want to sort my data with conditions that are not the Euclidean distance and retrieve the combination of points that resulted in the filtered data for plotting of the trajectory.

I was uncertain how to get my data back from the cells, but it's working fine now.

thanks again