This graphic was created with the help of the following Octave script: <source lang=Matlab> % Options

 frame_background_gray = true;

 if frame_background_gray
  graphics_toolkit("qt")         % has "insert text" option

% graphics_toolkit("fltk")  % has cursor coordinate readout

  frame_background = .94*[1 1 1];
  d  = 4;                         % amount to add to text sizes
 else
  graphics_toolkit("gnuplot")    % background will be white regardless of value below
  frame_background = .94*[1 1 1];
  d=0;
 endif
 
 xmax = 1000;                    % length of plots
 L    = 100;                     % length of rectangles

% (https://octave.org/doc/v4.2.1/Graphics-Object-Properties.html#Graphics-Object-Properties) % Speed things up when using Gnuplot

 set(0, "DefaultFigureColor",frame_background)
 set(0, "DefaultAxesTitleFontweight","normal")
 set(0, "DefaultAxesFontsize",12+d)   % size of numeric tick labels

% set(0, "DefaultTextFontsize",12+d)

 set(0, "DefaultAxesYlim",[0 2])
 set(0, "DefaultAxesXlim",0.02*([-200 xmax]))
 set(0, "DefaultAxesYtick",[])
 set(0, "DefaultLineLinewidth",2)

%=======================================================

 hfig = figure("position",[1 -150 735 835]);

 x1 = .02;                     % left margin
 x2 = .02;                     % right margin
 y1 = .08;                     % bottom margin for annotation
 y2 = .10;                     % top margin for title
 dy = .10;                     % vertical space between rows

 width = 1-x1-x2;
 height= (1-y1-y2-3*dy)/4;     % space allocated for each of 4 rows

 x_origin = x1;
 y_origin = 1;                 % start at top of graph area

%=======================================================

 y_origin = y_origin -y2 -height;        % position of top row
 subplot("position",[x_origin y_origin width height])

 f = [zeros(1,200) ones(1,L) zeros(1,100)];

 plot(0.02*([1:length(f)]-250), f ,"r" )
 title("h(t) (non-causal impulse response)", "fontsize",14+d)

%=======================================================

 y_origin = y_origin -dy -height;
 subplot("position",[x_origin y_origin width height])
 plot(0.02*([1:length(f)]-200), f, "b" )
 title("h(t-1) (causal impulse response)", "fontsize",14+d)

%=======================================================

 y_origin = y_origin -dy -height;
 subplot("position",[x_origin y_origin width height])
 a = [zeros(1,200) ones(1,L) zeros(1,250) 0.5*ones(1,100) zeros(1,250) 0.25*ones(1,100) zeros(1,200)];
 plot(0.02*([1:length(a)]-200), a,"m")
 ylim([0 2*max(a)])
 title("Input", "fontsize",14+d)

%=======================================================

 y_origin = y_origin -dy -height;
 subplot("position",[x_origin y_origin width height])
 b = conv(a,f);
 c = b(200:end);
 plot(0.02*([1:length(c)]-250), c, "r", 0.02*([1:length(c)]-200), c, "b")
 ylim([0 max(b)])
 legend("f(t) non-causal output", "f(t-1) (causal output)")
 title("Outputs", "fontsize",14+d)

</syntaxhighlight>