Octave Plot

>> figure;  % 図を表示するためのウィンドウを開く
>> hold on; % 続けて表示するようにする。
>> plot(1,1,'bo', 'MarkerSize', 10);
>> plot(2,2,'rx', 'MarkerSize', 10);
>> plot(3,3,'c+', 'MarkerSize', 10);
>> hold off; %解除

Octaveの精義―フリーの高機能数値計算ツールを使いこなす

初心者のためのGNUオクターブ入門: コマンドとグラフィックスの分かりやすい説明

> help plot
'plot' is a function from the file C:\Octave\Octave-4.2.0\share\octave\4.2.0\m\plot\draw\plot.m

 -- plot (Y)
 -- plot (X, Y)
 -- plot (X, Y, FMT)
 -- plot (..., PROPERTY, VALUE, ...)
 -- plot (X1, Y1, ..., XN, YN)
 -- plot (HAX, ...)
 -- H = plot (...)
     Produce 2-D plots.

     Many different combinations of arguments are possible.  The
     simplest form is

          plot (Y)

     where the argument is taken as the set of Y coordinates and the X
     coordinates are taken to be the range '1:numel (Y)'.

     If more than one argument is given, they are interpreted as

          plot (Y, PROPERTY, VALUE, ...)

     or

          plot (X, Y, PROPERTY, VALUE, ...)

     or

          plot (X, Y, FMT, ...)

     and so on.  Any number of argument sets may appear.  The X and Y
     values are interpreted as follows:

        * If a single data argument is supplied, it is taken as the set
          of Y coordinates and the X coordinates are taken to be the
          indices of the elements, starting with 1.

        * If X and Y are scalars, a single point is plotted.

        * 'squeeze()' is applied to arguments with more than two
          dimensions, but no more than two singleton dimensions.

        * If both arguments are vectors, the elements of Y are plotted
          versus the elements of X.

        * If X is a vector and Y is a matrix, then the columns (or rows)
          of Y are plotted versus X.  (using whichever combination
          matches, with columns tried first.)

        * If the X is a matrix and Y is a vector, Y is plotted versus
          the columns (or rows) of X.  (using whichever combination
          matches, with columns tried first.)

        * If both arguments are matrices, the columns of Y are plotted
          versus the columns of X.  In this case, both matrices must
          have the same number of rows and columns and no attempt is
          made to transpose the arguments to make the number of rows
          match.
>||
     Multiple property-value pairs may be specified, 
     but they must appear in pairs.  
     These arguments are applied to the line objects drawn by 'plot'.  

      Useful properties to modify are 

     "linestyle",
     "linewidth",
     "color",
     "marker",
     "markersize",
     "markeredgecolor",
     "markerfacecolor".  *Note Line Properties::.

     The FMT format argument can also be used to control the plot style.
     It is a string composed of four optional parts:
     "<linestyle><marker><color><;displayname;>". 

     When a marker is specified, 
     but no linestyle, only the markers are plotted.
     
     Similarly, if a linestyle is specified, 
     but no marker, then only lines are drawn.

     If both are specified then lines and markers will be plotted.  

     If no FMT and no PROPERTY/VALUE pairs are given,
     then the default plot style is solid lines with no markers 
     and the color determined by the "colororder" property of the current axes.

     Format arguments:

     linestyle

          '-'  Use solid lines (default).
          '--' Use dashed lines.
          ':'  Use dotted lines.
          '-.' Use dash-dotted lines.

     marker

          '+'  crosshair
          'o'  circle
          '*'  star
          '.'  point
          'x'  cross
          's'  square
          'd'  diamond
          '^'  upward-facing triangle
          'v'  downward-facing triangle
          '>'  right-facing triangle
          '<'  left-facing triangle
          'p'  pentagram
          'h'  hexagram

     color

          'k'  blacK
          'r'  Red
          'g'  Green
          'b'  Blue
          'y'  Yellow
          'm'  Magenta
          'c'  Cyan
          'w'  White

     ";displayname;"
          Here "displayname" is the label to use for the plot legend.

     The FMT argument may also be used to assign legend labels.  To do
     so, include the desired label between semicolons after the
     formatting sequence described above, e.g., "+b;Key Title;".  Note
     that the last semicolon is required and Octave will generate an
     error if it is left out.

     Here are some plot examples:

          plot (x, y, "or", x, y2, x, y3, "m", x, y4, "+")

     This command will plot 'y' with red circles, 'y2' with solid lines,
     'y3' with solid magenta lines, and 'y4' with points displayed as
     '+'.

          plot (b, "*", "markersize", 10)

     This command will plot the data in the variable 'b', with points
     displayed as '*' and a marker size of 10.

          t = 0:0.1:6.3;
          plot (t, cos(t), "-;cos(t);", t, sin(t), "-b;sin(t);");

     This will plot the cosine and sine functions and label them
     accordingly in the legend.

     If the first argument HAX is an axes handle, then plot into this
     axis, rather than the current axes returned by 'gca'.

     The optional return value H is a vector of graphics handles to the
     created line objects.

     To save a plot, in one of several image formats such as PostScript
     or PNG, use the 'print' command.

     See also: axis, box, grid, hold, legend, title, xlabel, ylabel,
     xlim, ylim, ezplot, errorbar, fplot, line, plot3, polar, loglog,
     semilogx, semilogy, subplot.

Additional help for built-in functions and operators is
available in the online version of the manual.  Use the command
'doc <topic>' to search the manual index.

Help and information about Octave is also available on the WWW
at http://www.octave.org and via the help@octave.org
mailing list.