please help , how to solve this error code

i wanna find coordinate of edge corner of label image,,

i have problem , i already process my image : http://tinypic.com/view.php?pic=2czer0o&s=6

and then this my image after process label : http://tinypic.com/view.php?pic=fbgcbm&s=6

but have message error :

? ?? Function 'find' is not defined for values of class 'cell'. Error in ==> mathcorner at 67 upperLeftCornerX = find(B(1,:), 1, 'first');

error found when i tried to find corner coordintae of label image .. this my label code :

[B,L] = bwboundaries(g,'holes');
    % Display the label matrix and draw each boundary
    imshow(label2rgb(L, @jet, [.1 .1 .1]))
    hold on
    for k = 1:length(B)
      boundary = B{k};
      plot(boundary(:,2), boundary(:,1), 'w', 'LineWidth', 1)
    end
%find coorndinate ,,
  upperLeftCornerX = find(B(1,:), 1, 'first');
  upperRightCornerX = find(B(1,:), 1, 'last');
  lowerLeftCornerX = find(B(end,:), 1, 'first');
  lowerRightCornerX = find(B(end,:), 1, 'last');
    upperLeftCornerX 
    upperRightCornerX 
    lowerLeftCornerX 
    lowerRightCornerX

Answer 1

[Malcolm Lidierth]

Use

{}

to access the cell contents not

()

as in the lines above with

B{k}