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\name{par}
\alias{par}
\alias{.Pars}
\alias{.Pars.readonly}
\title{Set or Query Graphical Parameters}

%% The real documentation is the code   in ../../../main/par.c
%% AND (defined AND commented)      in ../../../include/Graphics.h
%% Default initialization by GInit()    in ../../../main/par.c

\description{
  \code{par} can be used to set or query graphical parameters.
  Parameters can be set by specifying them as arguments to \code{par} in
  \code{tag = value} form, or by passing them as a list of tagged
  values.
}
\usage{
par(\dots, no.readonly = FALSE)

<highlevel plot> (\dots, <tag> = <value>)
}

\arguments{
  \item{\dots}{arguments in \code{tag = value} form, or a list of tagged
    values.  The tags must come from the graphical parameters described
    below.}
  \item{no.readonly}{logical; if \code{TRUE} and there are no other
    arguments, only parameters are returned which can be set by a
    subsequent \code{par()} call.}
}

\details{
  Parameters are queried by giving one or more character vectors to
  \code{par}.

  \code{par()} (no arguments) or \code{par(no.readonly=TRUE)} is used to
  get \emph{all} the graphical parameters (as a named list).  Their
  names are currently taken from the variable \code{.Pars}.
  \code{.Pars.readonly} contains the names of the \code{par} arguments
  which are \emph{readonly}.

  \emph{\bold{R.O.}} indicates \emph{\bold{read-only arguments}}: These
  may only be used in queries, i.e., they do \emph{not} set anything.

  All but these \emph{\bold{R.O.}} and the following
  \emph{\bold{low-level arguments}} can be set as well in high-level and
  mid-level plot functions, such as \code{\link{plot}},
  \code{\link{points}}, \code{\link{lines}}, \code{\link{axis}},
  \code{\link{title}}, \code{\link{text}}, \code{\link{mtext}}:
  \itemize{
    \item \code{"ask"}
    \item \code{"fig"}, \code{"fin"}
    \item \code{"mai"}, \code{"mar"}, \code{"mex"}
    \item \code{"mfrow"}, \code{"mfcol"}, \code{"mfg"}
    \item \code{"new"}
    \item \code{"oma"}, \code{"omd"}, \code{"omi"}
    \item \code{"pin"}, \code{"plt"}, \code{"ps"}, \code{"pty"}
    \item \code{"usr"}
    \item \code{"xlog"}, \code{"ylog"}
  }
}

\value{
  When parameters are set, their former values are returned in an
  invisible named list.  Such a list can be passed as an argument to
  \code{par} to restore the parameter values.
  Use \code{par(no.readonly = TRUE)} for the full list of parameters
  that can be restored.

  When just one parameter is queried, the value is a character string.
  When two or more parameters are queried, the result is a list of
  character strings, with the list names giving the parameters.

  Note the inconsistency: setting one parameter returns a list, but
  querying one parameter returns a vector.
}

\section{Graphical Parameters}{
  \describe{
    \item{\code{adj}}{The value of \code{adj} determines the way in
      which text strings are justified.  A value of \code{0} produces
      left-justified text, \code{0.5} centered text and \code{1}
      right-justified text.  (Any value in \eqn{[0, 1]} is allowed, and
      on most devices values outside that interval will also work.)
      Note that the \code{adj} argument of \code{\link{text}} also
      allows \code{adj = c(x, y)} for different adjustment in x- and y-
      direction.}
    \item{\code{ann}}{If set to \code{FALSE}, high-level plotting
      functions do not annotate the plots they produce with axis and
      overall titles.  The default is to do annotation.}
    \item{\code{ask}}{logical.  If \code{TRUE}, the user is asked for
      input, before a new figure is drawn.}
    \item{\code{bg}}{The color to be used for the background of plots.
      A description of how colors are specified is given below.}
    \item{\code{bty}}{A character string which determined the type of
      box which is drawn about plots.  If \code{bty} is one of
      \code{"o"}, \code{"l"}, \code{"7"}, \code{"c"}, \code{"u"}, or
      \code{"]"} the resulting box resembles the corresponding upper
      case letter.  A value of \code{"n"} suppresses the box.}
    \item{\code{cex}}{A numerical value giving the amount by which
      plotting text and symbols should be scaled relative to the
      default.}
    \item{\code{cex.axis}}{The magnification to be used for axis
      annotation relative to the current.}
    \item{\code{cex.lab}}{The magnification to be used for x and y
      labels relative to the current.}
    \item{\code{cex.main}}{The magnification to be used for main titles
      relative to the current.}
    \item{\code{cex.sub}}{The magnification to be used for sub-titles
      relative to the current.}
    \item{\code{cin}}{\emph{\bold{R.O.}}; character size
      \code{(width,height)} in inches.}
    \item{\code{col}}{A specification for the default plotting color.  A
      description of how colors are specified is given below.}
    \item{\code{col.axis}}{The color to be used for axis annotation.}
    \item{\code{col.lab}}{The color to be used for x and y labels.}
    \item{\code{col.main}}{The color to be used for plot main titles.}
    \item{\code{col.sub}}{The color to be used for plot sub-titles.}
    \item{\code{cra}}{\emph{\bold{R.O.}}; size of default character
      \code{(width,height)} in ``rasters'' (pixels).}
    \item{\code{crt}}{A numerical value specifying (in degrees) how
      single characters should be rotated.  It is unwise to expect
      values other than multiples of 90 to work.  Compare with
      \code{srt} which does string rotation.}
    \item{\code{csi}}{\emph{\bold{R.O.}}; height of (default sized)
      characters in inches.}
    \item{\code{cxy}}{\emph{\bold{R.O.}}; size of default character
      \code{(width,height)} in user coordinate units.
      \code{par("cxy")} is \code{par("cin")/par("pin")} scaled to user
      coordinates.
      Note that \code{c(\link{strwidth}(ch), \link{strheight}(ch))} for
      a given string \code{ch} is usually much more precise.}
    \item{\code{din}}{\emph{\bold{R.O.}}; the device dimensions in
      inches.}
    \item{\code{err}}{(\emph{Unimplemented}; \R is silent when points
      outside the plot region are \emph{not} plotted.)
      The degree of error reporting desired.}
    \item{\code{fg}}{The color to be used for the foreground of plots.
      This is the default color is used for things like axes and boxes
      around plots.  A description of how colors are specified is given
      below.}
    \item{\code{fig}}{A numerical vector of the form \code{c(x1, x2, y1,
    y2)} which gives the (NDC) coordinates of the figure region in
      the display region of the device.}
    \item{\code{fin}}{A numerical vector of the form \code{c(x, y)}
      which gives the size of the figure region in inches.}
    \item{\code{font}}{An integer which specifies which font to use for
      text.  If possible, device drivers arrange so that 1 corresponds
      to plain text, 2 to bold face, 3 to italic and 4 to bold italic.}
    \item{\code{font.axis}}{The font to be used for axis annotation.}
    \item{\code{font.lab}}{The font to be used for x and y labels.}
    \item{\code{font.main}}{The font to be used for plot main titles.}
    \item{\code{font.sub}}{The font to be used for plot sub-titles.}
    \item{\code{gamma}}{the gamma correction, see argument \code{gamma}
      to \code{\link{hsv}}.}
    \item{\code{lab}}{A numerical vector of the form \code{c(x, y, len)}
      which modifies the way that axes are annotated.  The values of
      \code{x} and \code{y} give the (approximate) number of tickmarks
      on the x and y axes and \code{len} specifies the label size.  The
      default is \code{c(5, 5, 7)}.
      \emph{Currently}, \code{len} \emph{is unimplemented}.}
    \item{\code{las}}{numeric in \{0,1,2,3\}; the style of axis labels.
      \describe{
    \item{0:}{always parallel to the axis [\emph{default}],}
    \item{1:}{always horizontal,}
    \item{2:}{always perpendicular to the axis,}
    \item{3:}{always vertical.}
      }
      Note that other string/character rotation (via argument \code{srt}
      to \code{par}) does \emph{not} affect the axis labels.
    }
    \item{\code{lty}}{The line type.
      Line types can either be specified as an integer (0=blank,
      1=solid, 2=dashed, 3=dotted, 4=dotdash, 5=longdash, 6=twodash) or
      as one of the character strings \code{"blank"}, \code{"solid"},
      \code{"dashed"}, \code{"dotted"}, \code{"dotdash"},
      \code{"longdash"}, or \code{"twodash"}, where \code{"blank"} uses
      `invisible lines' (i.e., doesn't draw them).

      Alternatively, a string of up to 8 characters (from \code{c(0:9,
    "A":"F")}) may be given, giving the length of line segments
      which are alternatively drawn and skipped.  See section `Line Type
      Specification' below.}
    \item{\code{lwd}}{The line width, a \emph{positive} number,
      defaulting to \code{1}.}
    \item{\code{mai}}{A numerical vector of the form \code{c(bottom,
    left, top, right)} which gives the margin size specified in
      inches.}
    \item{\code{mar}}{A numerical vector of the form \code{c(bottom,
    left, top, right)} which gives the lines of margin to be
      specified on the four sides of the plot.
      The default is \code{c(5, 4, 4, 2) + 0.1}.}
    \item{\code{mex}}{\code{mex} is a character size expansion factor
      which is used to describe coordinates in the margins of plots.}
    \item{\code{mfcol, mfrow}}{A vector of the form \code{c(nr, nc)}.
      Subsequent figures will be drawn in an \code{nr}-by-\code{nc}
      array on the device by \emph{columns} (\code{mfcol}), or
      \emph{rows} (\code{mfrow}), respectively.

      Consider the alternatives, \code{\link{layout}} and
      \code{\link{split.screen}}.
    }
    \item{\code{mfg}}{A numerical vector of the form \code{c(i, j)}
      where \code{i} and \code{j} indicate which figure in an array of
      figures is to be drawn next (if setting) or is being drawn (if
      enquiring).  The array must already have been set by \code{mfcol}
      or \code{mfrow}.

      For compatibility with S, the form \code{c(i, j, nr, nc)} is also
      accepted, when \code{nr} and \code{nc} should be the current
      number of rows and number of columns.  Mismatches will be ignored,
      with a warning.} 
    \item{\code{mgp}}{The margin line (in \code{mex} units) for the axis
      title, axis labels and axis line.
      The default is \code{c(3, 1, 0)}.}
    \item{\code{mkh}}{The height in inches of symbols to be drawn when
      the value of \code{pch} is an integer.
      %% <FIXME>
      \emph{Completely ignored currently}.
      %% </FIXME>
    }
    \item{\code{new}}{logical, defaulting to \code{FALSE}.  If set to
      \code{TRUE}, the next high-level plotting command (actually
      \code{\link{plot.new}}) should \emph{not clean} the frame before
      drawing ``as if it was on a \bold{\emph{new}} device''.}
    \item{\code{oma}}{A vector of the form \code{c(bottom, left, top,
    right)} giving the size of the outer margins in lines of text.}
    \item{\code{omd}}{A vector of the form \code{c(x1, x2, y1, y2)}
      giving the outer margin region in NDC (= normalized device
      coordinates), i.e., as fraction (in \eqn{[0,1]}) of the device
      region.}
    \item{\code{omi}}{A vector of the form \code{c(bottom, left, top,
    right)} giving the size of the outer margins in inches.}
    \item{\code{pch}}{Either an integer specifying a symbol or a single
      character to be used as the default in plotting points. }
    \item{\code{pin}}{The width and height of the current plot in
      inches.}
    \item{\code{plt}}{A vector of the form \code{c(x1, x2, y1, y2)}
      giving the coordinates of the plot region as fractions of the
      current figure region.}
    \item{\code{ps}}{integer; the pointsize of text and symbols.}
    \item{\code{pty}}{A character specifying the type of plot region to
      be used; \code{"s"} generates a square plotting region and
      \code{"m"} generates the maximal plotting region.}
    \item{\code{smo}}{(\emph{Unimplemented}) a value which indicates how
      smooth circles and circular arc should be.}
    \item{\code{srt}}{The string rotation in degrees.
      %% NOT true for R (but for S): Causes \code{srt} to be set to the
      %% same value.
    }
    \item{\code{tck}}{The length of tick marks as a fraction of the
      smaller of the width or height of the plotting region.  If
      \code{tck=1}, grid lines are drawn.  The default setting is to use
      \code{tcl=-0.5} (see below).}
    \item{\code{tcl}}{The length of tick marks as a fraction of the
      height of a line of text.  The default value is \code{-0.5}.}
    \item{\code{tmag}}{A number specifying the enlargement of text of
      the main title relative to the other annotating text of the plot.}
    \item{\code{type}}{character;  the default plot type desired, see
      \code{\link{plot.default}(type=\dots)}, defaulting to \code{"p"}.}
    \item{\code{usr}}{A vector of the form \code{c(x1, x2, y1, y2)}
      giving the extremes of the user coordinates of the plotting
      region.  When a logarithmic scale is in use (i.e.,
      \code{par("xlog")} is true, see below), then the x-limits will be
      \code{10 ^ par("usr")[1:2]}.  Similarly for the y-axis.
    }
    \item{\code{xaxp}}{A vector of the form \code{c(x1, x2, n)} giving
      the coordinates of the extreme tick marks and the number of
      intervals between tick-marks.}
    \item{\code{xaxs}}{The style of axis interval calculation to be used
      for the x-axis.  Possible values are \code{"r"}, \code{"i"},
      \code{"e"}, \code{"s"}, \code{"d"}.  The styles are generally
      controlled by the range of data or \code{xlim}, if given.
      Style \code{"r"} (regular) first extends the data range by 4
      percent and then finds an axis with pretty labels that fits within
      the range.
      Style \code{"i"} (internal) just finds an axis with pretty labels
      that fits within the original data range.
      Style \code{"s"} (standard) finds an axis with pretty labels
      within which the original data range fits.
      Style \code{"e"} (extended) is like style \code{"s"}, except that
      it is also ensured that there is room for plotting symbols within
      the bounding box.
      Style \code{"d"} (direct) specifies that the current axis should
      be used on subsequent plots.
      (\emph{Only \code{"r"} and \code{"i"} styles are currently
    implemented})}
    \item{\code{xaxt}}{A character which specifies the axis type.
      Specifying \code{"n"} causes an axis to be set up, but not
      plotted.  The standard value is \code{"s"}: for compatibility with
      S values \code{"l"} and \code{"e"} are accepted but are equivalent
      to \code{"s"}.}
    \item{\code{xlog}}{\emph{\bold{R.O.}}; logical value (see \code{log}
      in \code{\link{plot.default}}).  If \code{TRUE}, a logarithmic
      scale is in use (e.g., after \code{plot(*, log = "x")}).  For a
      new device, it defaults to \code{FALSE}, i.e., linear scale.}
    \item{\code{xpd}}{A logical value or \code{NA}.
      If \code{FALSE}, all plotting is clipped to the plot region, if
      \code{TRUE}, all plotting is clipped to the figure region, and if
      \code{NA}, all plotting is clipped to the device region.}
    \item{\code{yaxp}}{A vector of the form \code{c(y1, y2, n)} giving
      the coordinates of the extreme tick marks and the number of
      intervals between tick-marks.}
    \item{\code{yaxs}}{The style of axis interval calculation to be used
      for the y-axis.  See \code{xaxs} above.}
    \item{\code{yaxt}}{A character which specifies the axis type.
      Specifying \code{"n"} causes an axis to be set up, but not plotted.}
    \item{\code{ylog}}{\emph{\bold{R.O.}}; a logical value; see
      \code{xlog} above.}
  }
}

\section{Color Specification}{
  Colors can be specified in several different ways. The simplest way is
  with a character string giving the color name (e.g., \code{"red"}).  A
  list of the possible colors can be obtained with the function
  \code{\link{colors}}. Alternatively, colors can be specified directly in
  terms of there RGB components with a string of the form \code{"#RRGGBB"}
  where each of the pairs \code{RR}, \code{GG}, \code{BB} consist of two
  hexadecimal digits giving a value in the range \code{00} to \code{FF}.
  Colors can also be specified by giving an index into a small table of
  colors. This provides compatibility with S.

  The functions \code{rgb}, \code{hsv}, \code{gray} and \code{rainbow}
  provide additional ways of generating colors.}

\section{Line Type Specification}{
  Line types can either be specified by giving an index into a small
  built in table of line types (1 = solid, 2 = dashed, 3 = dotted) or
  directly as the lengths of on/off stretches of line.  This is done
  with a string of up to eight characters which give the lengths in
  consecutive positions in the string.  For example, the string
  \code{"33"} specifies three units on followed by three off and
  \code{"3313"} specifies three units on followed by three off followed
  by one on and finally three off.  The `units' here are (on most
  devices) proportional to \code{lwd}, and with \code{lwd = 1} are in
  pixels or points.
}

\note{
  The effect of restoring all the (settable) graphics parameters as
  in the examples is hard to predict if the device has been resized.
  Several of them are attempting to set the same things in different
  ways, and those last in the alphabet will win.  In particular, the
  settings of \code{mai}, \code{mar}, \code{pin}, \code{plt} and
  \code{pty} interact, as do the outer margin settings, the figure
  layout and figure region size.
}

\seealso{
  \code{\link{plot.default}} for some high-level plotting parameters;
  \code{\link{colors}}, \code{\link{gray}}, \code{\link{rainbow}},
  \code{\link{rgb}};
  \code{\link{options}} for other setup parameters;
  graphic devices \code{\link{x11}}, \code{\link{postscript}} and
  setting up device regions by \code{\link{layout}} and
  \code{\link{split.screen}}.
}

\examples{
op <- par(mfrow = c(2, 2), # 2 x 2 pictures on one plot
          pty = "s")       # square plotting region,
                           # independent of device size

## At end of plotting, reset to previous settings:
par(op)

## Alternatively,
op <- par(no.readonly = TRUE) # the whole list of settable par's.
## do lots of plotting and par(.) calls, then reset:
par(op)

par("ylog") # FALSE
plot(1 : 12, log = "y")
par("ylog") # TRUE

plot(1:2, xaxs = "i") # `inner axis' w/o extra space
stopifnot(par("xaxp")[1:2] == 1:2 &&
          par("usr") [1:2] == 1:2)

( nr.prof <-
  c(prof.pilots=16,lawyers=11,farmers=10,salesmen=9,physicians=9,
    mechanics=6,policemen=6,managers=6,engineers=5,teachers=4,
    housewives=3,students=3,armed.forces=1))
par(las = 3)
barplot(rbind(nr.prof)) # R 0.63.2: shows alignment problem
par(las = 0)# reset to default

ex <- function() {
   old.par <- par(no.readonly = TRUE) # all par settings which
                                      # could be changed.
   on.exit(par(old.par))
   ## ...
   ## ... do lots of par() settings and plots
   ## ...
   invisible() #-- now,  par(old.par)  will be executed
}
ex()
}

\keyword{iplot}
\keyword{dplot}
\keyword{environment}