R: S4: Present Talk Classes

talk-class {PBSmodelling}

R Documentation

S4: Present Talk Classes

Description

The function presentTalk is a tool that facilitates lectures and workshops in R. It allows the presenter to show code snippets alongside their execution, making use of R's graphical capabilities.

For presentTalk to work, six S4 class objects are created:

`talk`	root element that constitutes a talk;
`section`	branch element that defines a section within a talk;
`text`	leaf element that specifies text to be printed on the R console;
`file`	leaf element that specifies files to be opened by the OS;
`code`	leaf element that specifies R code to be executed;
`break`	leaf element that specifies where to allow a break in the talk.

The leaf elements, also termed primitive elements, occur in isolation and cannot contain other elements. Therefore, only two levels of nesting are supported: sections within a talk and primitives within a section.
See Appendix B in the PBSmodelling User's Guide for more information.

Details

This function uses a convenience function called xmlGetAttr (from the package XML) that retrieves the value of a named attribute in an XML node.

The function presentTalk translates the XML code into a list structure called .presentTalk below the global object .PBSmod. The GUI is represented as a list structure called presentwin under .PBSmod, as for all GUI objects in PBSmodelling.

Slots Available

talk
`name`	`character`	string giving the name of the talk (required)
`sections`	`list`	list of sections within the talk
`files`	`list`	list of files within the talk
section
`name`	`character`	string giving the name of the section (required)
`items`	`list`	list of the four primitive (leaf-element) S4 classes
`button`	`logical`	should GUI have a button that selects section?
`col`	`integer`	column in lower section of GUI to place button
`section_id`	`integer`	specify if section does not immediately follow a talk
text
`text`	`character`	text to display on the R console
`"break"`	`logical`	break the presentation after displaying the text specified?
file
`name`	`character`	string giving the name in the GUI for a group of files to open (required)
`filename`	`character`	individual file names associated with the group name in the GUI
`"break"`	`logical`	break the presentation after opening the group of files?
`button`	`logical`	should GUI add a button that opens this group of files?
`col`	`integer`	column in lower section of GUI to place button
code
`show`	`logical`	show the code snippet in the R console?
`print`	`logical`	print the results of running the R code?
`code`	`character`	the actual chunk of R code
`"break"`	`character`	string describing where to introduce breaks in the code segment
`eval`	`logical`	evaluate the R code?
break
`.xData`	`NULL`	allows a break in the talk for user interaction on the R console.

Creating S4 Objects

Objects can be created by calls of the form:

new("talk", name=name)
new("section",
  name     = node$attributes["name"],
  button   = as.logical(xmlGetAttr(node,"button",FALSE)),
  col      = as.integer(xmlGetAttr(node,"col",2)))
new("text", 
  text     = xmlValue(node),
  "break"  = as.logical(xmlGetAttr(node,"break",TRUE)))
new("file",
  name     = xmlGetAttr(node,"name",""), 
  "break"  = as.logical(xmlGetAttr(node,"break",TRUE)),
  filename = xmlValue(node),
  button   = as.logical(xmlGetAttr(node,"button",FALSE)),
  col      = as.integer(xmlGetAttr(node,"col",3)))
new("code",
  show     = as.logical(xmlGetAttr(node,"show",TRUE)), 
  print    = as.logical(xmlGetAttr(node,"print",TRUE)), 
  code     = xmlValue(node), 
  "break"  = tolower(xmlGetAttr(node,"break","print")))
new("break")

Author(s)

Alex Couture-Beil, Software Engineer
Earthly Technologies, Victoria BC