Trasferito da en.wikipedia su Commons da Maksim.

Io, detentore del copyright su quest'opera, la rilascio nel pubblico dominio. Questa norma si applica in tutto il mondo. In alcuni paesi questo potrebbe non essere legalmente possibile. In tal caso: Garantisco a chiunque il diritto di utilizzare quest'opera per qualsiasi scopo, senza alcuna condizione, a meno che tali condizioni siano richieste dalla legge.

function main() % Subderivative illustration

%  set up the plotting window, and some graphing paramenters
   figure(1); clf; hold on; axis equal; axis off;
   thick_line=2.5; thin_line=2; arrow_size=0.3; arrow_type=1; arrow_angle=20; %(angle in degrees)
   font_size=30; ball_rad=0.04;
   black=[0, 0, 0]; red=[1, 0, 0];

%  define the function; plot the x and y axes and the function
   a=-1.5; b=3; h=0.02; 
   X=[a  0 1 2 3]; Y=[0.3  0.2 0.5 1.5 3];
   arrow([a 0],       [b, 0],      thin_line, arrow_size, arrow_angle, arrow_type, black)  
   arrow([0, min(Y)-1], [0, max(Y)], thin_line, arrow_size, arrow_angle, arrow_type, black); 
   plot(X, Y, 'linewidth', thick_line); 

   % the "tangent" lines
   x0=X(3); y0=Y(3);
   s=0.8; plot(X, s*(X-x0)+y0, 'linewidth', thick_line, 'color', [1, 0, 0])
   s=0.5; plot(X, s*(X-x0)+y0, 'linewidth', thick_line, 'color', [1, 0, 0])

   % auxiliary line
   plot([x0 x0], [0, y0], 'linewidth', thin_line, 'color', [0, 0, 0], 'linestyle', '--')
   
%  graph some suggestive balls
   ball_full (x0, 0, ball_rad, [0 0 0 ]); 
   ball_full (x0, y0, ball_rad, [1 0 0 ]); 

%   text, sir
   H=text(x0, -0.006*font_size,  'x_0');
   set(H, 'fontsize', font_size, 'HorizontalAlignment', 'c', 'VerticalAlignment', 'c')

   axis(1.1*[a b min(Y)-1 max(Y)])
%  save to postscript
   saveas(gcf, 'Subderivative_illustration.eps', 'psc2')
   
function ball_full(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', 'none');


  function arrow(start, stop, thickness, arrow_size, sharpness, arrow_type, color)

% Function arguments:
% start, stop:  start and end coordinates of arrow, vectors of size 2
% thickness:    thickness of arrow stick
% arrow_size:   the size of the two sides of the angle in this picture ->
% sharpness:    angle between the arrow stick and arrow side, in degrees
% arrow_type:   1 for filled arrow, otherwise the arrow will be just two segments
% color:        arrow color, a vector of length three with values in [0, 1]
   
% convert to complex numbers
   i=sqrt(-1);
   start=start(1)+i*start(2); stop=stop(1)+i*stop(2);
   rotate_angle=exp(i*pi*sharpness/180);

% points making up the arrow tip (besides the "stop" point)
   point1 = stop - (arrow_size*rotate_angle)*(stop-start)/abs(stop-start);
   point2 = stop - (arrow_size/rotate_angle)*(stop-start)/abs(stop-start);

   if arrow_type==1 % filled arrow

      % plot the stick, but not till the end, looks bad
      t=0.5*arrow_size*cos(pi*sharpness/180)/abs(stop-start); stop1=t*start+(1-t)*stop;
      plot(real([start, stop1]), imag([start, stop1]), 'LineWidth', thickness, 'Color', color);

      % fill the arrow
      H=fill(real([stop, point1, point2]), imag([stop, point1, point2]), color);
      set(H, 'EdgeColor', 'none')
      
   else % two-segment arrow
      plot(real([start, stop]), imag([start, stop]),   'LineWidth', thickness, 'Color', color); 
      plot(real([stop, point1]), imag([stop, point1]), 'LineWidth', thickness, 'Color', color);
      plot(real([stop, point2]), imag([stop, point2]), 'LineWidth', thickness, 'Color', color);
   end

Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version.

Click on date to download the file or see the image uploaded on that date.

• (del) (cur) 20:04, 18 December 2005 . . en:User:Oleg_Alexandrov Oleg Alexandrov ( en:User_talk:Oleg_Alexandrov Talk) . . 540x463 (21025 bytes)

Questa immagine (categorizzazione automatica: math) o tutte le immagini in questa categoria o galleria dovrebbero essere ricreate usando grafica vettoriale come file SVG. Questo offre diversi vantaggi: vedi Commons:Media for cleanup per maggiori informazioni. Se è disponibile una versione in formato SVG di questa immagine, per favore caricala. Dopo aver caricato un file SVG, sostituisci questo avviso con il template {{Vector version available|nome_immagine.svg}}.