How to create a basic Langton’s Ant animation? how i set or find 'p' . SEE my ??? need help how to do this part

code:

% antdirection: 0 = east

% 90 = north

% 180 = west

% 270 = south

%

% gridcolor: 0 = white

% 1 = black

clear

close all

% initialize grid to all zeros (i.e., white)

gridcolor = zeros(100,100);

% specify the bounds of the grid

x_min = 1; x_max = 100;

y_min = 1; y_max = 100;

% initialize ant position to the middle of the grid

ant_x = 50;

ant_y = 50;

% initialize the ant direction to east

antdirection = 0;

% create initial plot with handle 'p', specifying the x and y values as

% ant_x and ant_y, set the marker type as a square and set erasemode to

% none so that all points are shown

p = ????????????;

% Set plot axis to span the grid

axis([0 100 0 100])

% specify the loop variable to indicate if the ant is still inside the grid

inside = 1;

% count the number of steps needed to reach the edge of the grid

total_steps = 0;

while inside == 1,

total_steps = total_steps + 1;

if gridcolor(ant_x,ant_y) == 0, % if the square is white, then

antdirection = antdirection + 90; % turn 90 deg to the right

else % otherwise the square is black, so

antdirection = antdirection - 90; % turn 90 deg to the left

end

% check antdirection and modify if necessary to keep it in the range of

% 0 to 360 degrees

if antdirection >= 360,

antdirection = antdirection - 360;

elseif antdirection < 0,

antdirection = antdirection + 360;

end

% the ant always flips the color of the square that it is on

gridcolor(ant_x,ant_y) = ~gridcolor(ant_x,ant_y);

if gridcolor(ant_x,ant_y) == 0, % if the grid square is white, then

% set the Marker edge and face color to white for the x,y point

set(p,??????????

else % the grid square is black, so

% set the Marker edge and face color to black for the x,y point

set(p,??????????

end

??????? % execute the graphics set immediately above

% determine the x and y direction of the ant motion (i.e., the position

% change for each coordinate)

ant_motion_x = cosd(antdirection);

ant_motion_y = sind(antdirection);

% move the ant to the next square

ant_x = ant_x + ant_motion_x;

ant_y = ant_y + ant_motion_y;

% determine if the ant has move outside the grid; if so, set inside to

% 0 so that the loop terminates

if (ant_x<x_min) || (ant_x>x_max),

inside = 0;

elseif (ant_y<y_min) || (ant_y>y_max),

inside = 0;

end

end