Error: Attempt to reference field of non-structure array

 The code:
 close all;clear all;clc;
 a=arduino('COM14');
 a.pinMode(2,'OUTPUT');
 a.pinMode(3,'OUTPUT');
 a.pinMode(4,'OUTPUT');
 a.pinMode(5,'OUTPUT');
 a.pinMode(9,'OUTPUT');
 a.pinMode(10,'OUTPUT');
 vid=videoinput('winvideo',1,'YUY2_160X120');
 set(vid,'TriggerRepeat',Inf);                
 vid.returnedcolorspace='rgb';
 vid.FrameGrabInterval=2;
 start(vid) %start the video aquisition here
 while(vid.FramesAcquired<=200) 
    data1=getdata(vid,1); 
    C=imrotate(data1,90);

    data=imcomplement(C);
    % Now to track yellow objects in real time
    % we have to subtract the yellow component 
    % from the grayscale image to extract the yellow components in the image.
    diff_im = imsubtract(data(:,:,3), rgb2gray(data)); 
    diff_im=medfilt2(diff_im,[1 2]);  % Use a median filter to filter out noise
    diff_im=im2bw(diff_im,0.26);      % Convert the resulting grayscale image into a binary image.
    diff_im=bwareaopen(diff_im,50);   % Remove all those pixels less than 50px
    bw=bwlabel(diff_im,8);            % Label all the connected components in the image.
    % This is where the image blob analysis occur.
    % Get a set of properties for each labeled region.
    stats=regionprops(bw,'BoundingBox','Centroid');
    % Display the image
    imshow(C)
     hold on
    % This is a loop to bound the yellow objects in a rectangular box and
    % along with its center coordinate
     for object=1:length(stats)
         bb=stats(object).BoundingBox;
         bc=stats(object).Centroid;
         rectangle('Position',bb,'EdgeColor','Y','LineWidth',2);
         plot(bc(1),bc(2),'-m+');
         a=text(bc(1)+15,bc(2), strcat('X:', num2str(round(bc(1))), 'Y:', num2str(round(bc(2)))));
         set(a, 'FontName', 'Arial', 'FontWeight', 'bold', 'FontSize', 12, 'Color', 'yellow');
         X=num2str(round(bc(1)));
         Y=num2str(round(bc(2)));
         if (X>61);
             a.digitalWrite(10, 1); 
             a.digitalWrite(4, 1);
             a.digitalWrite(5, 0);

         end
         if (X<59);
             a.digitalWrite(10, 1); 
             a.digitalWrite(4, 0);
             a.digitalWrite(5, 1);

         end
         if (X<=61);
              a.digitalWrite(9, 0);
              a.digitalWrite(10, 0);
         end
         if (X>=59);
             a.digitalWrite(9, 0);
             a.digitalWrite(10, 0);
         end

     end     
    hold off 
 end
stop(vid);       % Video acquisition is halted.
flushdata(vid);  % Removes all the processed image strored in RAM.
clear all

The output:

 Attempt to reference field of non-structure array
 Error in filename (line 51)
         a.digitalWrite(10, 1);

What I am trying to achieve here is to make the arduino gives the output when "if" conditions are met.

Answer 1

[the cyclist]

It looks like you redefined the variable a in this line

a=text(bc(1)+15,bc(2), strcat('X:', num2str(round(bc(1))), 'Y:', num2str(round(bc(2)))));

so that it is no longer the object coming out of the call to Arduino. Now it is a variable, and in the line that gives the error, you are treating that variable like a structure (which it is not).

[Aliff]

thx, i forgot i already used a for that.