?
 GNUPLOT is a command-driven interactive function plotting program.

 For help on any topic, type `help` followed by the name of the topic.

 The new GNUPLOT user should begin by reading the `introduction` topic
 (type `help introduction`) and about the `plot` command (type `help plot`).
 Additional help can be obtained from the USENET newsgroup
 comp.graphics.gnuplot.

?copyright
      Copyright (C) 1986 - 1993   Thomas Williams, Colin Kelley

   Permission to use, copy, and distribute this software and its
   documentation for any purpose with or without fee is hereby granted,
   provided that the above copyright notice appear in all copies and
   that both that copyright notice and this permission notice appear
   in supporting documentation.

   Permission to modify the software is granted, but not the right to
   distribute the modified code.  Modifications are to be distributed
   as patches to released version.

   This software is provided "as is" without express or implied warranty.


   AUTHORS

     Original Software:
       Thomas Williams,  Colin Kelley.

     Gnuplot 2.0 additions:
         Russell Lang, Dave Kotz, John Campbell.

     Gnuplot 3.0 additions:
         Gershon Elber and many others.

   There is a mailing list for gnuplot users. Note, however, that the
   newsgroup 
         comp.graphics.gnuplot 
   is identical to the mailing list (they
   both carry the same set of messages). We prefer that you read the
   messages through that newsgroup, to subscribing to the mailing list.
   (If you can read that newsgroup, and are already on the mailing list,
   please send a message info-gnuplot-request@dartmouth.edu, asking to be
   removed from the mailing list.)

   The address for mailing to list members is
         info-gnuplot@dartmouth.edu
   and for mailing administrative requests is 
         info-gnuplot-request@dartmouth.edu
   The mailing list for bug reports is 
         bug-gnuplot@dartmouth.edu
   The list of those interested in beta-test versions is
         info-gnuplot-beta@dartmouth.edu

?introduction
 GNUPLOT is a command-driven interactive function plotting program.
 It is case sensitive (commands and function names written in lowercase
 are not the same as those written in CAPS). All command names may be
 abbreviated, as long as the abbreviation is not ambiguous. Any number
 of commands may appear on a line, separated by semicolons (;).
 Strings are indicated with quotes.  They may be either single or double
 quotation marks, e.g.,

          load "filename"
          cd 'dir'

 Any command-line arguments are assumed to be names of files containing
 GNUPLOT commands, with the exception of standard X11 arguments, which
 are processed first. Each file is loaded with the `load` command, in the
 order specified. GNUPLOT exits after the last file is processed.  When
 no load files are named, gnuplot enters into an interactive mode.

 Commands may extend over several input lines, by ending each
 line but the last with a backslash (\). The backslash must be the LAST
 character on each line. The effect is as if the backslash and newline
 were not there. That is, no white space is implied, nor is a comment
 terminated. Therefore, commenting out a continued line comments out
 the entire command (see `comment`).

 In this documentation, curly braces ({}) denote optional arguments to
 many commands, and a vertical bar (|) separates mutually exclusive
 choices.  GNUPLOT keywords or help topics are indicated by backquotes
 or `boldface` (where available).  Angle brackets (<>) are used to mark
 replaceable tokens.

 For help on any topic, type `help` followed by the name of the topic.

 The new GNUPLOT user should begin by reading about the `plot`
 command (type `help plot`).
?cd
 The `cd` command changes the working directory.

 Syntax:
         cd ""

 The directory name must be enclosed in quotes.

 Examples:
         cd 'subdir'
         cd ".."
?clear
 The `clear` command erases the current screen or output device as
 specified by `set output`. This usually generates a formfeed on
 hardcopy devices. Use `set terminal` to set the device type.
?line-editing
?editing
?history
?command line-editing
 The Unix, Atari, VMS, MS-DOS and OS/2 versions of GNUPLOT support command
 line-editing.  Also, a history mechanism allows previous commands to be
 edited, and re-executed. After the command line has been edited, a newline
 or carriage return will enter the entire line regardless of where the
 cursor is positioned.

 The editing commands are as follows:

  `Line-editing`:

  ^B moves back a single character.
  ^F moves forward a single character.
  ^A moves to the beginning of the line.
  ^E moves to the end of the line.
  ^H and DEL delete the previous character.
  ^D deletes the current character.
  ^K deletes from current position to the end of line.
  ^L,^R redraws line in case it gets trashed.
  ^U deletes the entire line.
  ^W deletes the last word.

  `History`:

  ^P moves back through history.
  ^N moves forward through history.

 On the IBM PC the use of a TSR program such as DOSEDIT or CED may be
 desired for line editing. For such a case GNUPLOT may be compiled with
 no line editing capability (default makefile setup). Set READLINE in the
 makefile and add readline.obj to the link file if GNUPLOT line editing
 is to be used for the IBM PC. The following arrow keys may be used
 on the IBM PC and Atari versions if readline is used:

  Left  Arrow     - same as ^B.
  Right Arrow     - same as ^F.
  Ctl Left  Arrow - same as ^A.
  Ctl Right Arrow - same as ^E.
  Up    Arrow     - same as ^P.
  Down  Arrow     - same as ^N.

 The Atari version of readline defines some additional key aliases:

  Undo            - same as ^L.
  Home            - same as ^A.
  Ctrl Home       - same as ^E.
  ESC             - same as ^U.
  Help            - `help' plus return.
  Ctrl Help       - `help '.

 (The readline function in gnuplot is not the same as the readline used
 in GNU BASH and GNU EMACS.  It is somewhat compatible however.)
?comments
 Comments are supported as follows: a # may appear in most places in a line
 and GNUPLOT will ignore the rest of the line. It will not have this
 effect inside quotes, inside numbers (including complex numbers), inside
 command substitutions, etc. In short, it works anywhere it makes sense
 to work.
?environment
 A number of shell environment variables are understood by GNUPLOT.
 None of these are required, but may be useful.

 If GNUTERM is defined, it is used as the name of the terminal type to
 be used. This overrides any terminal type sensed by GNUPLOT on start
 up, but is itself overridden by the .gnuplot (or equivalent) start-up
 file (see `start-up`), and of course by later explicit changes.

 On Unix, AmigaDOS, AtariTOS, MS-DOS and OS/2, GNUHELP may be defined
 to be the pathname of the HELP file (gnuplot.gih).

 On VMS, the symbol GNUPLOT$HELP should be defined as the name of
 the help library for GNUPLOT.

 On Unix, HOME is used as the name of a directory to search for
 a .gnuplot file if none is found in the current directory.
 On AmigaDOS, AtariTOS, MS-DOS and OS/2, GNUPLOT is used. On VMS, SYS$LOGIN:
 is used. See `help start-up`.

 On Unix, PAGER is used as an output filter for help messages.

 On Unix, AtariTOS and AmigaDOS, SHELL is used for the `shell` command.
 On MS-DOS and OS/2, COMSPEC is used for the `shell` command.

 On AmigaDOS, GNUFONT is used for the screen font.  For example:
 "setenv GNUFONT sapphire/14".

 On MS-DOS, if the BGI interface is used, the variable `BGI` is used to point
 to the full path of the BGI drivers directory. Furthermore SVGA is used to
 name the Super VGA BGI driver in 800x600 res., and its mode of operation
 as 'Name.Mode'.
 E.g., if the Super VGA driver is C:\TC\BGI\SVGADRV.BGI and mode 3 is
 used for 800x600 res., then: 'set BGI=C:\TC\BGI' and 'set SVGA=SVGADRV.3'.
?exit
?quit
 The commands `exit` and `quit` and the END-OF-FILE character
 will exit GNUPLOT. All these commands will clear the output device
 (as the `clear` command does) before exiting.
?expressions
 In general, any mathematical expression accepted by C, FORTRAN,
 Pascal, or BASIC is valid. The precedence of these operators is
 determined by the specifications of the C programming language.
 White space (spaces and tabs) is ignored inside expressions.

 Complex constants may be expressed as the {,}, where 
 and  must be numerical constants. For example, {3,2}
 represents 3 + 2i; {0,1} represents `i` itself. The curly braces
 are explicitly required here.
?expressions functions
?functions
 The functions in GNUPLOT are the same as the corresponding functions
 in the Unix math library, except that all functions accept integer,
 real, and complex arguments, unless otherwise noted. The `sgn`
 function is also supported, as in BASIC.
?expressions functions abs
?functions abs
?abs
 The `abs` function returns the absolute value of its argument. The
 returned value is of the same type as the argument.

 For complex arguments, abs(x) is defined as the length of x in the
 complex plane [i.e.,  sqrt(real(x)**2 + imag(x)**2) ].
?expressions functions acos
?functions acos
?acos
 The `acos` function returns the arc cosine (inverse cosine) of its
 argument. `acos` returns its argument in radians.
?expressions functions arg
?functions arg
?arg
 The `arg` function returns the phase of a complex number, in radians.
?expressions functions asin
?functions asin
?asin
 The `asin` function returns the arc sin (inverse sin) of its argument.
 `asin` returns its argument in radians.
?expressions functions atan
?functions atan
?atan
 The `atan` function returns the arc tangent (inverse tangent) of its
 argument. `atan` returns its argument in radians.
?expressions functions besj0
?functions besj0
?besj0
 The `besj0` function returns the j0th Bessel function of its argument.
 `besj0` expects its argument to be in radians.
?expressions functions besj1
?functions besj1
?besj1
 The `besj1` function returns the j1st Bessel function of its argument.
 `besj1` expects its argument to be in radians.
?expressions functions besy0
?functions besy0
?besy0
 The `besy0` function returns the y0th Bessel function of its argument.
 `besy0` expects its argument to be in radians.
?expressions functions besy1
?functions besy1
?besy1
 The `besy1` function returns the y1st Bessel function of its argument.
 `besy1` expects its argument to be in radians.
?expressions functions ceil
?functions ceil
?ceil
 The `ceil` function returns the smallest integer that is not less than its
 argument. For complex numbers, `ceil` returns the smallest integer
 not less than the real part of its argument.
?expressions functions cos
?functions cos
?cos
 The `cos` function returns the cosine of its argument. `cos` expects its
 argument to be in radians.
?expressions functions cosh
?functions cosh
?cosh
 The `cosh` function returns the hyperbolic cosine of its argument.
 `cosh` expects its argument to be in radians.
?expressions functions erf
?functions erf
?erf
 The `erf` function returns the error function of the real part of
 its argument.
 If the argument is a complex value, the imaginary component is ignored.
?expressions functions erfc
?functions erfc
?erfc
 The `erfc` function returns 1.0 - the error function of the
 real part of its argument.
 If the argument is a complex value, the imaginary component is ignored.
?expressions functions exp
?functions exp
?exp
 The `exp` function returns the exponential function of its argument
 (`e` raised to the power of its argument).
?expressions functions floor
?functions floor
?floor
 The `floor` function returns the largest integer not greater than its
 argument. For complex numbers, `floor` returns the largest
 integer not greater than the real part of its argument.
?expressions functions gamma
?functions gamma
?gamma
 The `gamma` function returns the gamma function of the real part of
 its argument. For integer n, gamma(n+1) = n! .
 If the argument is a complex value, the imaginary component is ignored.
?expressions functions ibeta
?functions ibeta
?ibeta
 The `ibeta` function returns the incomplete beta function of the real
 parts of its arguments. p, q > 0 and x in [0:1]
 If the arguments are complex, the imaginary components are ignored.
?expressions functions inverf
?functions inverf
?inverf
 The `inverf` function returns the inverse error function of the real
 part of its argument.
?expressions functions igamma
?functions igamma
?igamma
 The `igamma` function returns the incomplete gamma function of the real
 parts of its arguments. a > 0 and x >= 0
 If the arguments are complex, the imaginary components are ignored.
?expressions functions imag
?functions imag
?imag
 The `imag` function returns the imaginary part of its argument as a
 real number.
?expressions functions invnorm
?functions invnorm
?invnorm
 The `invnorm` function returns the inverse normal distribution function
 of the real part of its argument.
?expressions functions int
?functions int
?int
 The `int` function returns the integer part of its argument, truncated
 toward zero.
?expressions functions lgamma
?functions lgamma
?lgamma
 The `lgamma` function returns the natural logarithm of the gamma
 function of the real part of its argument.
 If the argument is a complex value, the imaginary component is ignored.
?expressions functions log
?functions log
?log
 The `log` function returns the natural logarithm (base `e`) of its
 argument.
?expressions functions log10
?functions log10
?log10
 The `log10` function returns the logarithm (base 10) of its argument.
?expressions functions norm
?functions norm
?norm
 The `norm` function returns the normal distribution function
 (or Gaussian) of the real part of its argument.
?expressions functions rand
?functions rand
?rand
 The `rand` function returns a pseudo random number in the interval [0:1]
 using the real part of its argument as a seed. If seed < 0 the sequence
 is (re)initialized.
 If the argument is a complex value, the imaginary component is ignored.
?expressions functions real
?functions real
?real
 The `real` function returns the real part of its argument.
?expressions functions sgn
?functions sgn
?sgn
 The `sgn` function returns 1 if its argument is positive, -1 if its
 argument is negative, and 0 if its argument is 0. If the argument
 is a complex value, the imaginary component is ignored.
?expressions functions sin
?functions sin
?sin
 The `sin` function returns the sine of its argument. `sin` expects its
 argument to be in radians.
?expressions functions sinh
?functions sinh
?sinh
 The `sinh` function returns the hyperbolic sine of its argument. `sinh`
 expects its argument to be in radians.
?expressions functions sqrt
?functions sqrt
?sqrt
 The `sqrt` function returns the square root of its argument.
?expressions functions tan
?functions tan
?tan
 The `tan` function returns the tangent of its argument. `tan` expects
 its argument to be in radians.
?expressions functions tanh
?functions tanh
?tanh
 The `tanh` function returns the hyperbolic tangent of its argument.
 `tanh` expects its argument to be in radians.
?expressions operators
?operators
 The operators in GNUPLOT are the same as the corresponding operators
 in the C programming language, except that all operators accept
 integer, real, and complex arguments, unless otherwise noted.
 The ** operator (exponentiation) is supported, as in FORTRAN.

 Parentheses may be used to change order of evaluation.
?expressions operators binary
?operators binary
?binary
 The following is a list of all the binary operators and their
 usages:

  Symbol      Example      Explanation
   **          a**b          exponentiation
   *           a*b           multiplication
   /           a/b           division
   %           a%b         * modulo
   +           a+b           addition
   -           a-b           subtraction
   ==          a==b          equality
   !=          a!=b          inequality
   &           a&b         * bitwise AND
   ^           a^b         * bitwise exclusive OR
   |           a|b         * bitwise inclusive OR
   &&          a&&b        * logical AND
   ||          a||b        * logical OR
   ?:          a?b:c       * ternary operation

 (*) Starred explanations indicate that the operator requires
 integer arguments.

 Logical AND (&&) and OR (||) short-circuit the way they do in C.
 That is, the second && operand is not evaluated if the first is
 false; the second || operand is not evaluated if the first is true.

 The ternary operator evaluates its first argument (a). If it is
 true (non-zero) the second argument (b) is evaluated and returned,
 otherwise the third argument (c) is evaluated and returned.
?expressions operators unary
?operators unary
?unary
 The following is a list of all the unary operators and their
 usages:

  Symbol     Example      Explanation
   -           -a          unary minus
   ~           ~a        * one's complement
   !           !a        * logical negation
   !           a!        * factorial

 (*) Starred explanations indicate that the operator requires an
 integer argument.

 The factorial operator returns a real number to allow a greater range.
?help
 The `help` command displays on-line help. To specify information on a
 particular topic use the syntax:

         help {}

 If  is not specified, a short message is printed about
 GNUPLOT. After help for the requested topic is given, help for a
 subtopic may be requested by typing its name, extending the help
 request. After that subtopic has been printed, the request may be
 extended again, or simply pressing return goes back one level to the
 previous topic. Eventually, the GNUPLOT command line will return.
?load
 The `load` command executes each line of the specified input file as
 if it had been typed in interactively. Files created by the `save`
 command can later be `load`ed. Any text file containing valid
 commands can be created and then executed by the `load` command.
 Files being `load`ed may themselves contain `load` commands. See
 `comment` for information about comments in commands.

 The `load` command must be the last command on the line.

 Syntax:
         load ""

 The name of the input file must be enclosed in quotes.

 Examples:

         load 'work.gnu'
         load "func.dat"

 The `load` command is performed implicitly on any file names given as
 arguments to GNUPLOT. These are loaded in the order specified, and
 then GNUPLOT exits.
?pause
 The `pause` command displays any text associated with the command and
 then waits a specified amount of time or until the carriage return is
 pressed.  `pause` is especially useful in conjunction with `load` files.

 Syntax:
         pause  {""}

  may be any integer constant or expression. Choosing -1 will
 wait until a carriage return is hit, zero (0) won't pause at all, and
 a positive integer will wait the specified number of seconds.

 Note: Since `pause` is not part of the plot it may interact with
 different device drivers differently (depending upon how text and
 graphics are mixed).

 Examples:
         pause -1    # Wait until a carriage return is hit
         pause 3     # Wait three seconds
         pause -1  "Hit return to continue"
         pause 10  "Isn't this pretty?  It's a cubic-spline."

?plot
?splot
 `plot` and `splot` are the primary commands of the program. They plot
 functions and data in many, many ways. `plot` is used to plot 2-d
 functions and data, while `splot` plots 3-d surfaces and data.

 Syntax:

        plot {ranges} { | {"" {using ...}}}
                     {title} {style} {,  {title} {style}...}

        splot {ranges} { | {"" {index i} {using ...}}}
                     {title} {style} {,  {title} {style}...}

 where either a  or the name of a data file enclosed in quotes is
 supplied.  A function is a mathematical expression, or a pair (`plot`) or
 triple (`splot`) of mathematical expressions in the case of parametric
 functions.  User-defined functions and variables may also be defined here.

 `plot` and `splot` commands can be as simple as

         plot sin(x)

 and

         splot x * y

 or as complex as (!)

  plot [t=1:10] [-pi:pi*2] tan(t), "data.1" using 2:3 with lines,
        t**2 with points
?plot data-file
?plot datafile
?splot data-file
?splot datafile
?data-file
?datafile
?data
 Discrete data contained in a file can be displayed by specifying the
 name of the data file (enclosed in quotes) on the `plot` or `splot`
 command line. Data files should contain one data point per line.
 Lines beginning with # (or ! on VMS) will be treated as comments
 and ignored. For `plot`s, each data point represents an (x,y)
 pair. For `splot`s, each point is an (x,y,z) triple. For `plot`s with
 error bars (see `plot errorbars`), each data point is either
 (x,y,ydelta) or (x,y,ylow,yhigh). In all cases, the numbers on each
 line of a data file must be separated by blank space. This blank
 space divides each line into columns.

 For `plot`s the x value may be omitted, and for `splot`s the x
 and y values may be omitted. In either case the omitted values are
 assigned the current coordinate number. Coordinate numbers start at 0
 and are incremented for each data point read.

 To specify other formats, see `plot datafile using`.

 In the `plot` command, blank lines in the data file cause a break in
 the plot. There will be no line drawn between the preceding and
 following points if the plot style is `lines` or `linespoints` (see
 `plot style`). This does not change the plot style, as would plotting
 the data as separate curves.

 This example compares the data in the file population.dat to a
 theoretical curve:

         pop(x) = 103*exp((1965-x)/10)
         plot [1960:1990] 'population.dat', pop(x)

 The file population.dat might contain:

         # Gnu population in Antarctica since 1965
         1965   103
         1970   55
         1975   34
         1980   24
         1985   10

 When a data file is plotted, `samples` and `isosamples` are ignored.
 Curves plotted using the `plot` command are automatically extended to
 hold the entire curve. Similarly grid data plotted using the `splot`
 command is automatically extended, using the assumption that isolines
 are separated by blank lines (a line with only a CR/LF in it).

 Implicitly, there are two types of 3-d datafiles. If all the isolines
 are of the same length, the data is assumed to be a grid data, i.e.,
 the data has a grid topology. Cross isolines in the other parametric
 direction (the ith cross isoline passes through the ith point of all the
 provided isolines) will also be drawn for grid data. (Note contouring
 is available for grid data only.) If all the isolines are not of the
 same length, no cross isolines will be drawn and contouring that data
 is impossible.

 For splot, data files may contain more than one mesh and by default
 all meshes are plotted. Meshes are separated from each other, in the
 file, by double blank lines. To control and splot a single mesh from
 a multi mesh file, use the index modifier. See `splot index` for more.

 For splot if 3-d datafile and using format (see `splot datafile using`)
 specify only z (height field), a non parametric mode must be specified.
 If, on the other hand, x, y, and z are all specified, a parametric
 mode should be selected (see `set parametric`) since data is defining a
 parametric surface.

 A simple example of plotting a 3-d data file is

         set parametric
         splot 'glass.dat'

 or

         set noparametric
         splot 'datafile.dat'

 where the file datafile.dat might contain:

         # The valley of the Gnu.
         10
         10
         10

         10
         5
         10

         10
         1
         10

         10
         0
         10

 Note datafile.dat defines a 4 by 3 grid ( 4 rows of 3 points each ).
 Rows are separated by blank lines.

 On some computer systems with a popen function (UNIX), the datafile
 can be piped through a shell command by starting the file name
 with a '<'.  For example:

         pop(x) = 103*exp(-x/10)
         plot '< awk "{print $1-1965, $2}" population.dat', pop(x)

 would plot the same information as the first population example
 but with years since 1965 as the x axis.  If you want to execute
 this example, you have to delete all comments from the data file
 above or substitute the following command for the first part of the
 command above (the part up to the comma):

         plot '< awk "$0 !~ /^#/ {print $1-1965, $2}" population.dat'

 It is also possible to apply a single function to the "y" value only,
 e.g.

         plot 'population.dat' thru p(x)

 For more information about 3-d plotting, see `splot`.
?plot data-file using
?plot datafile using
?splot data-file using
?splot datafile using
?using
 The format of data within a file can be selected with the `using`
 option. An explicit scanf string can be used, or simpler column
 choices can be made.

 Syntax:

         plot "datafile" { using {  |
                                   : |
                                   :: |
                                   ::: |
                                   :::: }
                                 {""} } ...

 and

         splot "datafile" { using { :: |  }
                                  {""} } ...

 , , and  explicitly select the columns to plot from
 a space or tab separated multicolumn data file. If only  is
 selected for `plot`,  defaults to 1. If only  is selected
 for `splot`, then only that column is read from the file. An  of
 0 forces  to be plotted versus its coordinate number. ,
 , and  can be entered as constants or expressions.

 If errorbars (see also `plot errorbars`) are used for `plot`s,
 ydelta (for example, a +/- error) should be provided as the third
 column, or ylow and yhigh as third and fourth columns.

 If boxes or boxerrorbars are used for `plot`s, a fifth column to
 specify the width of the box may be given.  This implies that columns
 three and four must also be provided even if they are not used.
 If you want to plot boxes from a data file with three columns,
 set ylow and yhigh to y using the following command:
         plot "datafile" using 1:2:2:2:3 with boxes

 Scanf strings override any :(:) choices, except for
 ordering of input, e.g.,
         plot "datafile" using 2:1 "%f%*f%f"
 causes the first column to be y and the third column to be x.

 If the scanf string is omitted, the default is generated based on the
 :(:) choices. If the `using` option is omitted, "%f%f"
 is used for `plot` ("%f%f%f%f" for `errorbars` `plot`s) and "%f%f%f" is
 used for `splot`.

 Examples:

         plot "MyData" using "%*f%f%*20[^\n]%f" with lines

 Data are read from the file "MyData" using the format
 "%*f%f%*20[^\n]%f". The meaning of this format is: "%*f" ignore the
 first number, "%f" then read in the second and assign to x,
 "%*20[^\n]" then ignore 20 non-newline characters, "%f" then read in
 the y value.

         n=3;
         plot "MyData", "MyData" using n

 causes GNUPLOT to plot the second and third columns of MyData versus
 the first column. The command 'n=4; replot' would then plot the second
 and fourth columns of MyData versus the first column.

         splot "glass.dat" using 1

 causes GNUPLOT to plot the first coordinate of the points of glass.dat
 as the z coordinate while ignoring the other two coordinates.

 Note: GNUPLOT first reads a line of the data file into a buffer and
 then does a
         sscanf(input_buffer, scanf_string, &x, &y{, &z});
 where 'x', 'y', and 'z' are of type 'float'. Any scanf string that
 specifies two (three for `splot`, three or four for `errorbars`) float
 numbers may be used.
?plot errorbars
?errorbars
 Error bars are supported for 2-d data file plots by reading one or
 two additional columns specifying ydelta or ylow and yhigh
 respectively. No support exists for x error bars or any error bars
 for `splot`s.

 In the default situation, GNUPLOT expects to see three or four
 numbers on each line of the data file, either (x, y, ydelta) or
 (x, y, ylow, yhigh). The x coordinate must be specified. The order
 of the numbers must be exactly as given above. Data files in this
 format can easily be plotted with error bars:

         plot "data.dat" with errorbars

 The error bar is a vertical line plotted from (x, ylow) to (x,
 yhigh). If ydelta is specified instead of ylow and yhigh,
 ylow=y-ydelta and yhigh=y+ydelta are derived. If there
 are only two numbers on the line, yhigh and ylow are both set to
 y. To get lines plotted between the data points, `plot` the
 data file twice, once with errorbars and once with lines.

 If y autoscaling is on, the y range will be adjusted to fit the
 error bars.

 The `using` option may be used to specify how columns of the data file
 are to be assigned to x, y, ydelta, ylow, and yhigh. The x column must
 be provided and both the x and y columns must appear before the
 errorbar columns. If three column numbers are given, they are x, y,
 and ydelta. If four columns are given, they are x, y, ylow, and
 yhigh.

 Examples:

         plot "data.dat" using 1:2:3:4 with errorbars
         plot "data.dat" using 3:2:6 with errorbars
         plot "data.dat" using 3:4:8:7 with errorbars

 The first example reads, x, y, ylow, and yhigh, from columns 1, 2, 3,
 and 4. This is equivalent to the default.  The second example reads x
 from the third column, y from second and ydelta from the sixth column.
 The third example reads x from the third column, y from the fourth,
 ylow from the eighth, and yhigh from seventh columns.

 See also `plot using` and `plot style`.
?plot parametric
?splot parametric
?parametric
 When in parametric mode (`set parametric`) mathematical expressions must
 be given in pairs for `plot` and in triplets for `splot`:
         plot sin(t),t**2
 or
         splot cos(u)*cos(v),cos(u)*sin(v),sin(u)

 Data files are plotted as before, except any preceding parametric
 function must be fully specified before a data file is given as a
 plot. In other words, the x parametric function (sin(t) above) and
 the y parametric function (t**2 above) must not be interrupted with
 any modifiers or data functions; doing so will generate a syntax error
 stating that the parametric function is not fully specified.

 Ranges take on a different meaning when in parametric mode. The first
 range on the `plot` command is the `trange`, the next is the `xrange`,
 and the last is the `yrange`. For `splot` the order is `urange`,
 `vrange`, `xrange`, `yrange`, and finally `zrange`. The following
 `plot` command shows setting the `trange` to [-pi:pi], the `xrange` to
 [-1.3:1.3] and the `yrange` to [-1:1] for the duration of the plot:
         plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2

 Other modifiers, such as `with` and `title`, may be specified only
 after the parametric function has been completed:
         plot sin(t),t**2 title 'Parametric example' with linespoints


?splot ranges
?plot ranges
?ranges
 The optional range specifies the region of the plot that will be
 displayed.

 Ranges may be provided on the `plot` and `splot` command line and
 affect only that plot, or in the `set xrange`, `set yrange`, etc.,
 commands, to change the default ranges for future plots.

 Syntax:
         [{ =} { : }] { [{ : }] }

 where  is the independent variable (the defaults are x and
 y, but this may be changed with `set dummy`) and the min and max
 terms can be constant expressions.

 Both the min and max terms are optional. The ':' is also optional
 if neither a min nor a max term is specified. This allows '[ ]' to
 be used as a null range specification.

 Specifying a range in the `plot` command line turns autoscaling for
 that axis off for that plot. Using one of the `set` range commands
 turns autoscaling off for that axis for future plots, unless changed
 later. (See `set autoscale`).

 Examples:

 This uses the current ranges:
         plot cos(x)

 This sets the x range only:
         plot [-10:30] sin(pi*x)/(pi*x)

 This is the same, but uses t as the dummy-variable:
         plot [t = -10 :30]  sin(pi*t)/(pi*t)

 This sets both the x and y ranges:
         plot [-pi:pi] [-3:3]  tan(x), 1/x

 This sets only the y range, and turns off autoscaling on both axes:
         plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)

 This sets xmax and ymin only:
         plot [:200] [-pi:]  exp(sin(x))

 This sets the x, y, and z ranges:
         splot [0:3] [1:4] [-1:1] x*y
?splot index
?index
 Splotting of multi mesh data files can be controlled via the index modifier.
 A data file can contain more than one mesh, and in that case all meshes
 in the file will be splotted by default. Meshes are separated from each
 other, in the data file, by double blank lines. To splot a single mesh in
 a multi mesh file use the index modifier which specify which mesh to splot.
 First mesh is mesh 0.

 Example:

 splot "data1" index 2 with points

 will splot the third mesh in file data1 with points.
?plot style
?splot style
?style
?plot with
?with
 Plots may be displayed in one of eight styles: `lines`, `points`,
 `linespoints`, `impulses`, `dots`, `errorbars`, `steps`, `boxes`, or
 `boxerrorbars`.  The `lines` style connects adjacent points with lines.
 The `points` style displays a small symbol at each point.
 The `linespoints` style does both `lines` and `points`.
 The `impulses` style displays a vertical line from the x axis
 (or from the grid base for `splot`) to each point. The `dots` style
 plots a tiny dot at each point; this is useful for
 scatter plots with many points.

 The `errorbars` style is only relevant to 2-d data file plotting. It
 is treated like `points` for `splot`s and function `plot`s. For data
 `plot`s, `errorbars` is like `points`, except that a vertical error
 bar is also drawn: for each point (x,y), a line is drawn from
 (x,ylow) to (x,yhigh). A tic mark is placed at the ends of the error
 bar. The ylow and yhigh values are read from the data file's columns,
 as specified with the `using` option to plot. See `plot errorbars` for
 more information.

 The `boxes` style is only relevant to 2-d plotting.  Another style
 called `boxerrorbars` is also available and is only relevant to 2-d
 data file plotting.  This style is a combination of the `boxes` and
 `errorbars` styles.  The `boxes` style draws a box centred about
 the given x coordinate from the yaxis to the given y coordinate.
 The width of the box is obtained in one of three ways.  First, if a 
 data file has a fifth column, this will be used to set the width of 
 the box. Columns 3 and 4 (for `boxerrorbars`) are necessary but
 ignored in this instance.  Secondly, if a width has been set using 
 the `set boxwidth` command, this will be used.  Otherwise the width 
 of each box will be calculated automatically so that it touches the
 adjacent boxes.

 The `steps` style is only relevant to 2-d plotting.  This style
 connects consecutive points with two line segments: the first
 from (x1,y1) to (x2,y1) and the second from (x2,y1) to (x2,y2).

 Default styles are chosen with the `set function style` and
 `set data style` commands.

 By default, each function and data file will use a different
 line type and point type, up to the maximum number of available
 types. All terminal drivers support at least six different point
 types, and re-use them, in order, if more than six are required.
 The LaTeX driver supplies an additional six point types (all variants
 of a circle), and thus will only repeat after twelve curves are
 plotted with points.

 If desired, the style and (optionally) the line type and point type
 used for a curve can be specified.

 Syntax:

         with