Graph and geometric objects attributes

### 18.1.2 Graph and geometric objects attributes

There are two kinds of attributes for graphs and geometric objects: global attributes of a graphic scene and individual attributes for the specific geometric objects in the scene.

#### Individual attributes

Graphic attributes are optional arguments of the form display=value. They must be given as the last argument of a graphic instruction. Attributes are ordered in several categories: color, point shape, point width, line style, line thickness, legend value, position and presence. In addition, surfaces may be filled or not, 3D surfaces may be filled with a texture, 3D objects may also have properties with respect to the light. Attributes of different categories may be combined with +, e.g. in:

plotfunc(x^2+y^2,[x,y],display=red+line_width_3+filled)

The graphic attributes are:

Color
  which is set with display=value or color=value, where value is a nonnegative integer. See Section 18.1.3 for more details on colors. The predefined colors in Xcas are: black, white, red, blue, green, magenta, cyan, yellow, brown, purple, violet, pink, orange, grey, teal, olive, navy, and gold.
Point shape
  which is set with display=value, where value can be one of: rhombus_point, plus_point, square_point, cross_point, triangle_point, star_point, point_point or invisible_point.
Point width
  which is set with display=value. The values can be:

  point_width_n where n is an integer between 1 and 7.

Line thickness
  which is set with thickness=n or display=line_width_n where n is an integer between 1 and 7.
Line shape
  which is set with display=value, where value can be one of: dash_line, solid_line, dashdot_line, dashdotdot_line, cap_flat_line, cap_square_line or cap_round_line.
Legend
  where the text is set with legend="legendname" and the position is set with display=value, where value is quadrantn for some n∈{1,2,3,4}. These values correspond to the position of the legend of the object (using the trigonometric plane conventions). The legend is not displayed if the attribute display=hidden_name is added.
Filling
  which is set with display=filled.
Image texture
  which is set gl_texture="picture_filename" and fills a surface with a texture. See the interface manual for a more complete description and for gl_material options.

#### Examples

(See Section 25.9.3, Section 25.5.2, Section 25.3.3 and Section 25.6.3 for information on the commands used.)

polygon(-1,-i,1,2*i,legend="P")

point(1+i,legend="hello")

color(segment(0,1+i),red)

By entering

segment(0,1+i,color=red)

we get the same result as above.

#### Global attributes

The following attributes are pertinent to the scene as a whole:

- axes=true or axes=false shows or hides the axes. Alternatively, axes=a can be used, where a is a nonnegative integer. The following values have effect:
  - a=1: the same as axes=true.
  - a=0: the same as axes=false.
  - a=2: show only the relevant portion of the ordinate (used for bar plots).
  - a=3: show the outer frame/ticks but not the green and red inner axes (similar to Matlab).
  - a=4: same as a=3, but the ordinate ticks are not shown (used for drawing multi-channel waveforms and power spectra, where y-values are not meaningful or significant).
- title="titlename" sets the title.
- labels=["xname","yname","zname"] sets names of the x,y,z axes.
- gl_x_axis_name="xname", gl_y_axis_name="yname", gl_z_axis_name="zname" sets the names of the axes individually.
- legend=["xunit","yunit","zunit"] sets units for the axes.
- gl_x_axis_unit="xunit", gl_y_axis_unit="yunit", gl_z_axis_unit="zunit" sets units for the axes individually.
- gl_texture="filename" sets the background image to filename.
- gl_x=xmin..xmax, gl_y=ymin..ymax, gl_z=zmin..zmax sets the graphic configuration (do not use for interactive scenes)
- gl_xtick=xmark, gl_ytick=ymark, gl_ztick=zmark sets the tick marks for the axes.
- gl_shownames=true or gl_shownames=false shows or hides objects names
- gl_rotation=[x,y,z] defines the rotation axis for the animation rotation of 3D scenes.
- gl_quaternion=[x,y,z,t] defines the quaternion for the visualization in 3D scenes (do not use for interactive scenes).
- a few other OpenGL light configuration options are available but not described here.

#### Examples

title="median_line";triangle(-1-i,1,1+i);median_line(-1-i,1,1+i); median_line(1,-1-i,1+i);median_line(1+i,1,-1-i)

labels=["u","v"];plotfunc(u+1,u)

#### Formatting textual annotations

There are several formatting options for the textual attributes (title, labels, and legend). Note that they can be used only in 2D plots.

- "*This is bold*" draws the text in a bold sans serif font.
- "/This is italic/" draws the text in an italic sans serif font.
- "$This is mathmode$" draws the text in a serif font and enables the following mathematical typesetting options:
  - ^int, where int is an integer, prints int in the exponent (this is also functional outside math mode).
  - @char, where char is a letter, draws char with slanted font (useful for variables in formulas).
  - -- (two hyphens) prints as a minus sign − (which is different than the ordinary hyphen!).
  - <= resp. >= prints as ≤ resp. ≥.
  - +- resp. -+ prints as ± resp. ∓.
  - == prints as ≡.
  - != prints as ≠.
  - \/ prints as √ . Note that the backslash must be escaped, i.e. entered as \\.
  - -> prints as →.
  - => prints as ⇒.
  - ** prints as ⋯ (vertically centered dots).
  - *, when preceded/followed by an alphanumeric character or parenthesis, is printed as · (the multiplication dot).

Note that changing font to bold, italic or serif typeface can only be applied to the entire text. The @-option uses special slanted Unicode symbols.

#### Example

axes=0; legend(i,"*This is bold text*"); legend(.5i,"/This is italic text/"); legend(1.5i,"Spectral energy density [W/m^3]"); legend(1+1.5i,"$pi^2/6 = 1^-2 + 2^-2 + 3^-2 + ** (Basel problem)$"); legend(1+i,"$@f(@x) = 1 -- @x -- @x^2 = 0 => @x = --(1 +- \\/5)/2$"); s1:="alpha*sin(@x--beta) + beta*cos(@x--alpha) <= alpha + beta":; s2:="alpha, beta > 0":; legend(1+.5i,"$"+s1+" for "+s2+"$")