add_label

Context: labels

Synopsis

Creates a label.

Syntax

add_label([id,] xpos, ypos, text [,attributes])

Labels can also be created directly from the GUI using the "Annotate"
menu item.

Description

The function arguments.

Argument	Description
id	A ChipsId structure identifying the item.
xpos, ypos	The location of the label; the current coordinate system is used if the "coordsys" attribute is not set. The halign and valign attributes control the location of the label relative to the label text.
text	The text of the label, which can include LaTeX formatting statements.
attributes	Configure object properties by giving an attribute string (a space-separated list of key=value pairs), list, dictionary, or a ChIPS object.

The add_label command creates a label whose attributes are specified by user preferences or in an attribute list. The new label becomes current by default; providing a ChipsId overrides the currency state.

The position of the label is specified as a coordinate pair (xpos, ypos) in data, pixel, frame, or plot normalized coordinates using the 'coordsys' attribute. Labels specified in data coordinates will only be displayed if the are within the coordinate system range.

Alignment

Alignment attributes control how the text string is situated in relation to the reference position. Horizontal alignment can be specified as left (0), center (.5), right (1), or a numeric ratio of the text length. Vertical alignment is similarly controlled: bottom (0), center (.5), top (1), or a numeric ratio.

Customizing the Label

There are several attributes that control the label characteristics. The attributes can be set to the ChIPS defaults, values provided in the add_label command, or values from the user's preference file.

The attributes may also be modified with the set_label command at any time; see "ahelp set_label" and "ahelp setget" for more information.

Please see the section "Label Preferences and Attributes" below the examples for a list of the label preferences.

Examples

Example 1

chips> add_label(0.4, 0.5, 'area={\\pi}r^2')

Add a label at position (.4,.5). Latex formatting is used in the label text, so the "\" character had to be protected. Alternatively, the r qualifier could have been used:

chips> add_label(0.4, 0.5, r'area={\pi}r^2')

Example 2

chips> add_label(100, 100, "Fig. B", ["color", "blue", "size", 14])

Create a blue label, specifying the attribute values in a list.

Example 3

chips> clear()
chips> add_curve([1,2,3], [-9,2,-2])
chips> add_label(2, -6, "In data coordinates")
chips> add_label(0.5, 0.92, "Frame coords", ["halign", 0.5, "coordsys",
FRAME_NORM])
chips> add_label(0.1, 0.9, "Plot coords", ["coordsys", PLOT_NORM])
chips> limits(X_AXIS, 1.5, 4)

Three labels are added: the first is placed in the data-coordinate system created by the add_curve call; the second is placed in frame-normalized coordinates, and so appears as a plot title (the text has been horizontally aligned so that its center is at the middle of the frame); and the third is placed in plot-normalized coordinates (so appears at the top-left corner of the plot). The limits call causes only the first label to move; the second and third labels do not change position.

Example 4

chips> lbl = ChipsLabel()
chips> lbl.color = "blue"
chips> lbl.size = 8
chips> lbl.stem = "MyLabel"
chips> add_label(100, 100, "Figure A", lbl)

Populate the "lbl" structure with the attribute values, then add the label "Figure A".

Example 5

chips> l = ChipsLabel()
chips> l.coordsys = FRAME_NORM
chips> l.halign = 1
chips> import time
chips> add_label(0.95, 0.05, time.asctime(), l)

A label is added to the bottom-right corner of the frame (the text is right-aligned since halign=1) which contains the current time.

Label Preferences and Attributes

The attributes associated with labels are given in the following table, where the "Set?" column refers to whether the attribute can be changed using the set_label() command. To change the label preference settings prepend "label." to the attribute name.

Attribute	Description	Options	Default	Set?
angle	Angle, in degrees, at which the label is drawn	-360.0 to 360.0	0.0	Yes
color	Color of the text	name or hex; see the Color section of "ahelp chipsopt"	default	Yes
coordsys	coordinate system for the label	PIXEL, WINDOW_NORM, FRAME_NORM, PLOT_NORM, DATA	see "ahelp coordsys"	No
depth	Integer value indicating label depth	see the Depth section of "ahelp chipsopt"	default	Yes
font	text font	helvetica\|courier\|times\|greek; see the Font section of "ahelp chipsopt"	helvetica	Yes
fontstyle	style of the label text	normal\|bold\|italic\|bolditalic; see the Font Style section of "ahelp chipsopt"	normal	Yes
halign	Horizontal location of the string reference point of the label	auto\|base\|center\|left\|right\|top; see the Text Alignment section of "ahelp chipsopt"	left	Yes
size	Font size of the text	1 to 100	12	Yes
stem	stem used for label id	An alpha-numeric character sequence that does not contain a space	lbl	No
valign	Vertical location of the string reference point of the label	auto\|base\|center\|left\|right\|top; see the Text Alignment section of "ahelp chipsopt"	base	Yes

Bugs

See the bugs pages on the ChIPS website for an up-to-date listing of known bugs.