xfig starts the graphics device driver for producing XFig
  (version 3.2) graphics.
The auxiliary function ps.options can be used to set and view
  (if called without arguments) default values for the arguments to
  xfig and postscript.
xfig(file = if(onefile) "Rplots.fig" else "Rplot%03d.fig",
     onefile = FALSE, encoding = "none",
     paper = "default", horizontal = TRUE,
     width = 0, height = 0, family = "Helvetica",
     pointsize = 12, bg = "transparent", fg = "black",
     pagecentre = TRUE, defaultfont = FALSE, textspecial = FALSE)a character string giving the name of the file.   For use
    with onefile = FALSE give a C integer format such as
    "Rplot%03d.fig" (the default in that case).
    (See postscript for further details.)
logical: if true allow multiple figures in one file. If false, assume only one page per file and generate a file number containing the page number.
The encoding in which to write text strings.  The
    default is not to re-encode.  This can be any encoding recognized by
    iconv: in a Western UTF-8 locale you probably want to
    select an 8-bit encoding such as latin1, and in an East Asian
    locale an EUC encoding.  If re-encoding fails, the text
    strings will be written in the current encoding with a warning.
the size of paper region.  The choices
    are "A4", "Letter" and "Legal" (and these
    can be lowercase).  A further choice is "default", which
    is the default.  If this is selected, the papersize is taken
    from the option "papersize" if that is set to a non-empty
    value, otherwise "A4".
the orientation of the printed image, a logical. Defaults to true, that is landscape orientation.
the width and height of the
    graphics region in inches.  The default is to use the entire
    page less a 0.5 inch overall margin in each direction.  (See
    postscript for further details.)
the font family to be used.  This must be one
    of "AvantGarde", "Bookman", "Courier",
    "Helvetica" (the default), "Helvetica-Narrow",
    "NewCenturySchoolbook", "Palatino" or
    "Times".  Any other value is replaced by
    "Helvetica", with a warning.
the default point size to be used.
the initial background color to be used.
the initial foreground color to be used.
logical: should the device region be centred on the page?
logical: should the device use xfig's default font?
logical: should the device set the textspecial flag for all text elements. This is useful when generating pstex from xfig figures.
This section describes the implementation of the conventions for graphics devices set out in the “R Internals Manual”.
The default device size is the paper size with a 0.25 inch border on all sides.
Font sizes are in big points.
The default font family is Helvetica.
Line widths are integers, multiples of 5/432 inch.
Circle radii are multiples of 1/1200 inch.
Colours are interpreted by the viewing/printing application.
Although xfig can produce multiple plots in one file, the XFig
  format does not say how to separate or view them.  So
  onefile = FALSE is the default.
The file argument is interpreted as a C integer format as used
  by sprintf, with integer argument the page number.
  The default gives files Rplot001.fig, …, Rplot999.fig,
  Rplot1000.fig, ….
Line widths as controlled by par(lwd =) are in multiples of
  5/6*1/72 inch.  Multiples less than 1 are allowed.  pch = "." with
  cex = 1 corresponds to a square of side 1/72 inch.
Windows users can make use of WinFIG (http://www.schmidt-web-berlin.de/WinFIG.htm, shareware), or XFig under Cygwin.