function main()    thickness1=2; thickness2=1; arrowsize=5; arrow_type=2; ball_rad=0.012;    blue=[0, 0, 1]; fontsize=25; dist=0.005;        a=-1.4; b=-a;    h=0.01;    X=a:h:b;    Y=zeros(length(X), 1);    for i=1:length(X)       x=X(i);       if x < 1 & x > -1 	 Y(i)=exp(-1/(1-x^2));       end    end      figure(1);  clf; hold on; axis equal; axis off arrow([a 0], [b+0.2, 0], thickness2, arrowsize, pi/8,arrow_type, [0, 0, 0]) arrow([0 -0.1], [0 2.*max(Y)], thickness2, arrowsize, pi/8,arrow_type, [0, 0, 0]) plot(X, Y, 'linewidth', thickness1, 'color', [0 0 1]); arrow([b+0.1 0], [b+0.2, 0], thickness2, arrowsize, pi/8,arrow_type, [0, 0, 0])  ball(1, 0, ball_rad, blue); ball(-1, 0, ball_rad, blue); place_text_smartly(1, fontsize, 6, dist, '1'); place_text_smartly(-1, fontsize, 6, dist, '-1');  saveas(gcf, 'mollifier_illustration.eps', 'psc2')  function place_text_smartly (z, fs, pos, d, tx)  p=cos(pi/4)+sqrt(-1)*sin(pi/4);  z = z + p^pos * d * fs;   shiftx=0.0003;  shifty=0.002;  x = real (z); y=imag(z);   H=text(x+shiftx*fs, y+shifty*fs, tx); set(H, 'fontsize', fs, 'HorizontalAlignment', 'c', 'VerticalAlignment', 'c')  function ball(x, y, r, color)    Theta=0:0.1:2*pi;    X=r*cos(Theta)+x;    Y=r*sin(Theta)+y;    H=fill(X, Y, color);    set(H, 'EdgeColor', color);  function arrow(start, stop, thickness, arrowsize, sharpness, arrow_type, color)  %  draw a line with an arrow at the end %  start is the x,y point where the line starts %  stop is the x,y point where the line stops %  thickness is an optional parameter giving the thickness of the lines    %  arrowsize is an optional argument that will give the size of the arrow  %  It is assumed that the axis limits are already set %  0 < sharpness < pi/4 determines how sharp to make the arrow %  arrow_type draws the arrow in different styles. Values are 0, 1, 2, 3.     %       8/4/93    Jeffery Faneuff %       Copyright (c) 1988-93 by the MathWorks, Inc. %       Modified by Oleg Alexandrov 2/16/03         if nargin <=6       color=[0, 0, 0];    end        if (nargin <=5)       arrow_type=0;   % the default arrow, it looks like this: ->    end        if (nargin <=4)       sharpness=pi/4; % the arrow sharpness - default = pi/4    end     if nargin<=3       xl = get(gca,'xlim');       yl = get(gca,'ylim');       xd = xl(2)-xl(1);                   yd = yl(2)-yl(1);                   arrowsize = (xd + yd) / 2;   % this sets the default arrow size    end     if (nargin<=2)       thickness=0.5; % default thickness    end            xdif = stop(1) - start(1);    ydif = stop(2) - start(2);     if (xdif == 0)       if (ydif >0)  	 theta=pi/2;       else 	 theta=-pi/2;       end    else       theta = atan(ydif/xdif);  % the angle has to point according to the slope    end     if(xdif>=0)       arrowsize = -arrowsize;    end     if (arrow_type == 0) % draw the arrow like two sticks originating from its vertex       xx = [start(1), stop(1),(stop(1)+0.02*arrowsize*cos(theta+sharpness)),NaN,stop(1),... 	    (stop(1)+0.02*arrowsize*cos(theta-sharpness))];       yy = [start(2), stop(2), (stop(2)+0.02*arrowsize*sin(theta+sharpness)),NaN,stop(2),... 	    (stop(2)+0.02*arrowsize*sin(theta-sharpness))];       plot(xx,yy, 'LineWidth', thickness, 'color', color)    end     if (arrow_type == 1)  % draw the arrow like an empty triangle       xx = [stop(1),(stop(1)+0.02*arrowsize*cos(theta+sharpness)), ... 	    stop(1)+0.02*arrowsize*cos(theta-sharpness)];       xx=[xx xx(1) xx(2)];              yy = [stop(2),(stop(2)+0.02*arrowsize*sin(theta+sharpness)), ... 	    stop(2)+0.02*arrowsize*sin(theta-sharpness)];       yy=[yy yy(1) yy(2)];        plot(xx,yy, 'LineWidth', thickness, 'color', color)        %     plot the arrow stick       plot([start(1) stop(1)+0.02*arrowsize*cos(theta)*cos(sharpness)], [start(2), stop(2)+ ... 		    0.02*arrowsize*sin(theta)*cos(sharpness)], 'LineWidth', thickness, 'color', color)           end        if (arrow_type==2) % draw the arrow like a full triangle       xx = [stop(1),(stop(1)+0.02*arrowsize*cos(theta+sharpness)), ... 	    stop(1)+0.02*arrowsize*cos(theta-sharpness),stop(1)];              yy = [stop(2),(stop(2)+0.02*arrowsize*sin(theta+sharpness)), ... 	    stop(2)+0.02*arrowsize*sin(theta-sharpness),stop(2)];        %     plot the arrow stick       plot([start(1) stop(1)+0.01*arrowsize*cos(theta)], [start(2), stop(2)+ ... 		    0.01*arrowsize*sin(theta)], 'LineWidth', thickness, 'color', color)       H=fill(xx, yy, color);% fill with black       set(H, 'EdgeColor', 'none')     end     if (arrow_type==3) % draw the arrow like a filled 'curvilinear' triangle       curvature=0.5; % change here to make the curved part more curved (or less curved)       radius=0.02*arrowsize*max(curvature, tan(sharpness));       x1=stop(1)+0.02*arrowsize*cos(theta+sharpness);       y1=stop(2)+0.02*arrowsize*sin(theta+sharpness);       x2=stop(1)+0.02*arrowsize*cos(theta)*cos(sharpness);       y2=stop(2)+0.02*arrowsize*sin(theta)*cos(sharpness);       d1=sqrt((x1-x2)^2+(y1-y2)^2);       d2=sqrt(radius^2-d1^2);       d3=sqrt((stop(1)-x2)^2+(stop(2)-y2)^2);       center(1)=stop(1)+(d2+d3)*cos(theta);       center(2)=stop(2)+(d2+d3)*sin(theta);        alpha=atan(d1/d2);       Alpha=-alpha:0.05:alpha;       xx=center(1)-radius*cos(Alpha+theta);       yy=center(2)-radius*sin(Alpha+theta);       xx=[xx stop(1) xx(1)];       yy=[yy stop(2) yy(1)];  %     plot the arrow stick       plot([start(1) center(1)-radius*cos(theta)], [start(2), center(2)- ... 		    radius*sin(theta)], 'LineWidth', thickness, 'color', color);        H=fill(xx, yy, color);% fill with black       set(H, 'EdgeColor', 'none')     end