R Interface to MetaPost

Description

Provides an R interface to METAPOST. There are functions to generate an R description of a MetaPost curve, functions to generate MetaPost code from an R description, functions to process MetaPost code, and functions to read solved MetaPost paths back into R.

Details

Generate a MetaPost path with functions like knot.

Write the MetaPost path to a file with metapost.

Run mpost on the file with mpost.

Read the solved path (Bezier control points) into R with mptrace.

Draw a solved path with grid.metapost.

It is also possible to pass grid.metapost the original path (and it will perform the write/solve/read steps itself).

Author(s)

Paul Murrell <paul@stat.auckland.ac.nz>

References

Hobby, J. D. and the MetaPost development team (2018). METAPOST a user's manual. https://www.tug.org/docs/metapost/mpman.pdf

See Also

knot metapost mpost mptrace grid.metapost

Examples

oldunits <- options(metapost.units="in")
p <- knot(0, 0) + dir(0) + dir(0) + knot(1, 1)
grid.metapost(p)
options(oldunits)

Draw a MetaPost curve.

Description

Draw a MetaPost curve in grid graphics.

Usage

## S3 method for class 'mppath'
metapostGrob(x, gp = gpar(), name = NULL, digits=2, ...)
## S3 method for class 'mpcontrols'
metapostGrob(x, gp = gpar(), name = NULL, ...)
## S3 method for class 'mpcontrolList'
metapostGrob(x, gp = gpar(), name = NULL, ...)
grid.metapost(...)

Arguments

Value

metapostGrob creates a "metapostgrob" object.

Author(s)

Paul Murrell

See Also

knot, mptrace.

Examples

oldunits <- options(metapost.units="in")
p <- knot(0, 0) + dir(0) + dir(0) + knot(1, 1) 
grid.metapost(p)
options(oldunits)

Create a MetaPost Path

Description

These functions can be used to describe a MetaPost path, consisting of two or more knots, with various constraints on how the path behaves between the knots.

Usage

knot(x, y, units = getOption("metapost.units"),
     dir = NA, dir.left = dir, dir.right = dir,
     cp.left.x = NA, cp.right.x = NA, cp.left.y = NA, cp.right.y = NA,
     curl.left = NA, curl.right = NA,
     tension.left = NA, tension.right = NA)
cp(x, y, units = getOption("metapost.units"))
curl(x)
cycle()
dir(x, y = NULL)
tension(x)

Arguments

Details

A MetaPost path is constructed using calls to knot and combining the results using the + operator (see the examples below).

Constraints for a knot can be specified within the call to knot or by combining connectors (cp, dir, etc) with a knot using +.

Knots can also be combined using - (a straight line rather than a curve), %+% (no inflection), and %-% (straight line with smooth connection) operators.

Value

The individual functions generate knots and connectors, but when combined together, they produce a MetaPost path ("mppath") object.

Author(s)

Paul Murrell

References

Hobby, J. D. and the MetaPost development team (2018). METAPOST a user's manual. https://www.tug.org/docs/metapost/mpman.pdf

See Also

metapost, mpost, mptrace, grid.metapost.

Examples

knot(0, 0, dir.right=0)
knot(0, 0, dir.right=0) + knot(1, 1)
knot(0, 0) + dir(0) + knot(1, 1)

Generate a MetaPost File

Description

Generate a MetaPost file from a MetaPost path.

Usage

metapost(x, file = "fig.mp", digits=2)

Arguments

Value

The MetaPost code is returned invisibly.

Author(s)

Paul Murrell

See Also

knot

Examples

p <- knot(0, 0) + dir(0) + dir(0) + knot(1, 1)
mpcode <- metapost(p, NULL)
mpcode

Run mpost on a MetaPost File

Description

Run mpost on a MetaPost file, possibly with additional options.

Usage

mpost(file = "fig.mp",
      cmd = NULL, template = NULL, format = NULL, tracing = TRUE)

Arguments

Details

By default, tracing is TRUE, which produces a log file that can be read into R using mptrace.

Both output and log files will be produced in the same directory as the file.

Value

Used for its side effect of producing output files and log files.

Author(s)

Paul Murrell

See Also

metapost, mptrace

Examples

oldunits <- options(metapost.units="in")
p <- knot(0, 0) + dir(0) + dir(0) + knot(1, 1)
mpfile <- file.path(tempdir(), "fig.mp")
metapost(p, mpfile)
mpost(mpfile)
options(oldunits)

Parse mpost Log Files

Description

Read a log file generated by mpost (possibly via mpost) to obtain solved MetaPost path information (which can then be drawn by grid.metapost).

Usage

mptrace(logfile = "fig.log")
mpbbox(psfile)
mpvp(psfile, ...)

Arguments

Details

The log file must have been generated by mpost with tracingchoices=1 (possibly using mpost(..., tracing=TRUE)).

The functions mpbbox and mpvp parse a PostScript file that was generated by mpost, returning the bounding box of the output and a viewport based on that bounding box respectively.

Value

A list of Bezier control points (mpcontrols objects).

Author(s)

Paul Murrell

See Also

mpost, grid.metapost

Examples

oldunits <- options(metapost.units="in")
oldwd <- setwd(tempdir())
p <- knot(0, 0) + dir(0) + dir(0) + knot(1, 1)
metapost(p, "fig.mp")
mpost("fig.mp")
paths <- mptrace("fig.log")
grid.metapost(paths)
setwd(oldwd)
options(oldunits)