plot

Arguments

x

vector or matrix of real numbers or integers. If omitted, it is assumed to be the vector 1:n where n is the number of curve points given by the y parameter.

y

vector or matrix of real numbers or of integers.

func

handle of a function, as in plot(x, sin). If the function to plot needs some parameters as input arguments, the function and its parameters can be specified through a list as in plot(x, list(delip,-0.4))

polynomial

Single polynomial or array of polynomials.

rational

Single rational or array of rationals.

y1, y2, y3,..

Can be any of the possible input types described above:

• vectors or matrices of real numbers or of integers
• handle of a function (possibly in a list with its parameters).
• polynomials
• rationals

LineSpec

This optional argument must be a string that will be used as a shortcut to specify a way of drawing a line. We can have one LineSpec per y or {x,y} previously entered. LineSpec options deals with LineStyle, Marker and Color specifiers (see LineSpec). Those specifiers determine the line style, mark style and color of the plotted lines.

GlobalProperty

This optional argument represents a sequence of couple statements {PropertyName,PropertyValue} that defines global objects' properties applied to all the curves created by this plot. For a complete view of the available properties (see GlobalProperty).

logflag

"ln" | "nl" | "ll" : 2-character word made of "l" standing for "Logarithmic" or/and "n" standing for "Normal". The first character applies to the X axis, the second to the Y axis. Hence, "ln" means that the X axis is logarithmic and the Y axis is normal. The default is "nn": both axes in normal scales.

logflag must be used after axes_handle (if any) and before the first curve's data x or y or func. It applies to all curves drawn by the plot(…) instruction.

axes_handle

This optional argument forces the plot to appear inside the selected axes given by axes_handle rather than the current axes (see gca).

Description

plot plots a set of 2D curves. plot has been rebuild to better handle Matlab syntax. To improve graphical compatibility, Matlab users should use plot (rather than plot2d).

Data entry specification :

In this paragraph and to be more clear, we won't mention LineSpec nor GlobalProperty optional arguments as they do not interfere with entry data (except for "Xdata", "Ydata" and "Zdata" property, see GlobalProperty). It is assumed that all those optional arguments could be present too.

If y is a vector, plot(y) plots vector y versus vector 1:size(y,'*').

If y is a matrix, plot(y) plots each columns of y versus vector 1:size(y,1).

If x and y are vectors, plot(x,y) plots vector y versus vector x. x and y vectors should have the same number of entries.

If x is a vector and y a matrix plot(x,y) plots each columns of y versus vector x. In this case the number of columns of y should be equal to the number of x entries.

If x and y are matrices, plot(x,y) plots each columns of y versus corresponding column of x. In this case the x and y sizes should be the same.

Finally, if only x or y is a matrix, the vector is plotted versus the rows or columns of the matrix. The choice is made depending on whether the vector's row or column dimension matches the matrix row or column dimension. In case of a square matrix (on x or y only), priority is given to columns rather than lines (see examples below).

When it is necessary and possible, plot transposes x and y, to get compatible dimensions; a warning is then issued. For instance, when x has as many rows as y has columns. If y is square, it is never transposed.

y can also be a function defined as a macro or a primitive. In this case, x data must be given (as a vector or matrix) and the corresponding computation y(x) is done implicitly.

The LineSpec and GlobalProperty arguments should be used to customize the plot. Here is a complete list of the available options.

LineSpec

This option may be used to specify, in a short and easy manner, how the curves are drawn. It must always be a string containing references to LineStyle, Marker and Color specifiers.

These references must be set inside the string (order is not important) in an unambiguous way. For example, to specify a red long-dashed line with the diamond mark enabled, you can write : 'r--d' or '--dire' or '--reddiam' or another unambiguous statement... or to be totally complete 'diamondred--' (see LineSpec).

Note that the line style and color, marks color (and sizes) can also be (re-)set through the polyline entity properties (see polyline_properties).

GlobalProperty

This option may be used to specify how all the curves are plotted using more option than via LineSpec. It must always be a couple statement constituted of a string defining the PropertyName, and its associated value PropertyValue (which can be a string or an integer or... as well depending on the type of the PropertyName). Using GlobalProperty, you can set multiple properties : every properties available via LineSpec and more : the marker color (foreground and background), the visibility, clipping and thickness of the curves. (see GlobalProperty)

Note that all these properties can be (re-)set through the polyline entity properties (see polyline_properties).

Remarks

By default, successive plots are superposed. To clear the previous plot, use clf(). To enable auto_clear mode as the default mode, edit your default axes doing:

da=gda();

da.auto_clear = 'on'

For a better display plot function may modify the box property of its parent Axes. This happens when the parent Axes were created by the call to plot or were empty before the call. If one of the axis is centered at origin, the box is disabled. Otherwise, the box is enabled.

For more information about box property and axis positioning see axes_properties

A default color table is used to color plotted curves if you do not specify a color. When drawing multiple lines, the plot command automatically cycles through this table. Here are the used colors:

Enter the command plot to see a demo.

Examples

Choosing the normal or logarithmic plotting mode:

gda().grid = [1 1]*color("grey70");
title(gda(), "fontsize", 3, "color", "lightseagreen", "fontname", "helvetica bold");

x = linspace(1e-1,100,1000);
xm = 35;
dx = 17;
G = exp(-((x-xm)/dx).^2/2)*30;

scf(1); clf
subplot(2,2,1), plot(x, G),       title("plot(x, y)")
subplot(2,2,2), plot("ln", x, G), title("semilog-x : plot(""ln"", x, y)"); gca().sub_ticks(1) = 8;
subplot(2,2,3), plot("nl", x, G), title("semilog-y : plot(""nl"", x, y)"); gca().sub_ticks(2) = 8;
subplot(2,2,4), plot("ll", x, G), title("loglog : plot(""ll"", x, y)");    gca().sub_ticks = [8 8];

sda();

Simple plot of a single curve:

// Default abscissae = indices
subplot(1,2,1)
plot(sin(0:0.1:2*%pi))
xlabel("x indices")

// With explicit abscissae:
x = [0:0.1:2*%pi]';
subplot(1,2,2)
plot(x, sin(x))
xlabel("Specified abscissae")

Multiple curves with shared abscissae: Y: 1 column = 1 curve:

clf
x = [0:0.1:2*%pi]';
plot(x, [sin(x) sin(2*x) sin(3*x)])

Specifying a macro or a builtin instead of explicit ordinates:

clf
subplot(2,2,1)         // sin() is a builtin
plot(1:0.1:10, sin)    // <=> plot(1:0.1:10, sin(1:0.1:10))
title("plot(x, sin)", "fontsize",3)

// with a macro:
deff('y = myFun(x)','y = x + rand(x)')
subplot(2,2,2)
plot(-3:0.1:5, myFun)
title("plot(x, myFun)", "fontsize",3)

// With functions with parameters:
subplot(2,2,3)
plot(1:0.05:7, list(delip, -0.4))  // <=> plot(1:0.05:7, delip(1:0.05:7,-0.4) )
title("plot(x, list(delip,-0.4))", "fontsize",3)

function Y=myPow(x, p)
    [X,P] = ndgrid(x,p);
    Y = X.^P;
    m = max(abs(Y),"r");
    for i = 1:size(Y,2)
        Y(:,i) = Y(:,i)/m(i);
    end
endfunction
x = -5:0.1:6;
subplot(2,2,4)
plot(x, list(myPow,1:5))
title("plot(x, list(myPow,1:5))", "fontsize",3)

Plotting the graph of polynomials or rationals:

clf
s = %s;

// Polynomials
x = -0.5:0.02:3;
p = s*[2 ; (s-2) ; (s-1)*(s-2)]
subplot(1,2,1)
plot(x, p)
legend(prettyprint(p,"latex","",%t), 2);

// Rationals
x = -0.5:0.02:2;
r = (s-1)*s/(s-7)./[s+1, s-4]
subplot(1,2,2)
plot(x, r)
legend(prettyprint(r,"latex","",%t), 2);

gcf().children.grid = color("grey70")*[1 1]; // grids
gcf().children.children([1 3]).font_size=3;  // legends

--> p = s*[2 ; (s-2) ; (s-1)*(s-2)]
 p  =
  2s
  -2s +s²
  2s -3s² +s³

../..
--> r = (s-1)*s/(s-7)./[s+1, s-4]
 r  =
     -s +s²      -s +s²
   ----------  -----------
   -7 -6s +s²  28 -11s +s²

Setting curves simple styles when calling plot():

clf
t = -%pi:%pi/20:2*%pi;
// sin() : in Red, with O marks, without line
// cos() : in Green, with + marks, with a solid line
// gaussian: in Blue, without marks, with dotted line
gauss = 1.5*exp(-(t/2-1).^2)-1;

plot(t,sin,'ro', t,cos,'g+-', t,gauss,':b')

Vertical segments between two curves, with automatic colors, and using Global properties for markers styles. Targeting a defined axes.

clf
subplot(1,3,3)
ax3 = gca();         // We will draw here later
xsetech([0 0 0.7 1]) // Defines the first Axes area
t = -3:%pi/20:7;
// Tuning markers properties
plot([t ;t],[sin(t) ;cos(t)],'marker','d','markerFaceColor','green','markerEdgeColor','yel')

// Targeting a defined axes
plot(ax3, t, sin)

Case of a non-square Y matrix: When it is consistent and required, X or/and Y data are automatically transposed in order to become plottable.

clf()
x = [5 6 7 8]
y = [1   1   1   1   8
     2   3   4   5   9
     3   4   5   6  10
     4   5   6   7  12];

// Only one matching possibility case: how to make 4 identical plots in 4 manners...
// x is 1x4 (vector) and y is 4x5 (non square matrix)
subplot(221); plot(x', y , "o-");    // OK as is
subplot(222); plot(x , y , "o-");    // x is transposed
subplot(223); plot(x', y', "o-");    // y is transposed
subplot(224); plot(x , y', "o-");    // x and y are transposed

Case of a square Y matrix, and X implicit or square:

clf
t = [1   1   1   1
     2   3   4   5
     3   4   5   6
     4   5   6   7];

subplot(231), plot(t,"o-") , title("plot(t)",  "fontsize",3)
subplot(234), plot(t',"o-"), title("plot(t'')", "fontsize",3)

subplot(232), plot(t,t,"o-") , title("plot(t, t)",  "fontsize",3)
subplot(233), plot(t,t',"o-"), title("plot(t,t'')", "fontsize",3)

subplot(235), plot(t', t,"o-"),  title("plot(t'', t)",   "fontsize",3)
subplot(236), plot(t', t',"o-"), title("plot(t'', t'')", "fontsize",3)

for i=1:6, gcf().children(i).data_bounds([1 3]) = 0.5; end

Special cases of a matrix X and a vector Y:

clf
X = [1   1   1   1
     2   3   4   5
     3   4   5   6
     4   5   6   7];
y = [1 2 3 4];

subplot(221), plot(X, y,  "o-"), title("plot(X, row)",  "fontsize",3)
        // equivalent to plot(t, [1 1 1 1; 2 2 2 2; 3 3 3 3; 4 4 4 4])
subplot(223), plot(X, y', "o-"), title("plot(X, col)  (row = col'')",  "fontsize",3)
subplot(222), plot(X',y,  "o-"), title("plot(X'', row)",  "fontsize",3)
subplot(224), plot(X',y', "o-"), title("plot(X'', col)  (row = col'')",  "fontsize",3)

for i = 1:4, gcf().children(i).data_bounds([1 3]) = 0.5; end

Post-tuning Axes and curves:

x=[0:0.1:2*%pi]';
plot(x-4,sin(x), x+2,cos(x))

// axis centered at (0,0)
a=gca(); // Handle on axes entity
a.x_location = "origin";
a.y_location = "origin";

// Some operations on entities created by plot ...
isoview on
a.children // list the children of the axes : here it is an Compound child composed of 2 entities
poly1= a.children.children(2); //store polyline handle into poly1
poly1.foreground = 4;  // another way to change the style...
poly1.thickness = 3;   // ...and the thickness of a curve.
poly1.clip_state='off' // clipping control
isoview off

See also

• plot2d — 2D plot
• plot2d2 — 2D plot (step function)
• plot2d3 — 2D plot (vertical bars)
• plot2d4 — 2D plot (arrows style)
• param3d — plots a single curve in a 3D cartesian frame
• surf — 3D surface plot
• scf — set the current graphic figure (window)
• clf — Clears and resets a figure or a frame uicontrol
• close — Closes graphic figures, progression or wait bars, the help browser, xcos, the variables browser or editor.
• delete — delete a graphic entity and its children.
• LineSpec — to quickly customize the lines appearance in a plot
• Named colors — list of named colors
• GlobalProperty — customizes the objects appearance (curves, surfaces...) in a plot or surf command

History