A powerful and elegant high-level data visualization system inspired by Trellis graphics, with an emphasis on multivariate data. Lattice is sufficient for typical graphics needs, and is also flexible enough to handle most nonstandard requirements. See ?Lattice for an introduction.
Lattice is a powerful and elegant high-level data visualization system for R, inspired by Trellis graphics. It is designed with an emphasis on multivariate data, and in particular allows easy conditioning to produce "small multiple" plots. Lattice is sufficient for typical graphics needs, and is also flexible enough to handle most nonstandard requirements.
o The primary goal of the 0.20 series is to further improve documentation, building up to an eventual 1.0 release. Specific major changes are given below.
o Use dev.hold()/dev.flush() introduced in R 2.14.0 for smoother displays and transition.
o It is now easier to use raster images in levelplot() by specifying top-level argument 'useRaster=TRUE'.
o 'pos' can now be a vector in ltext(), just as it can in text().
o Explicit components in 'colorkey' (for levelplot()) to specify graphical parameters of boundary and tick marks/labels.
o "spline" added as a possibly 'type' in panel.xyplot(), following a suggestion from Patrick Breheny.
o Support for traditional graphics-like log scale annotation, using 'scales=list(equispaced.log = FALSE)'.
o parallel() deprecated in favour of parallelplot(), to avoid potential confusion with the parallel package.
o The internal lattice.status list is cleaned up whenever new page starts. This should fix lattice bug #1629.
o There is a new option to provide a custom rule for computing default breakpoints in histogram(). See ?histogram for details.
o New datasets USMortality and USRegionalMortality.
o The primary goal of the 0.19 series is to improve documentation and fix some obscure but long-standing bugs, building up to an eventual 1.0 release. Specific major changes are given below.
o Added new arguments 'grid' and 'abline' in panel.xyplot().
o Added a "panel.background" setting.
o Restructured storage of plot-specific information, fixing bug reported in https://stat.ethz.ch/pipermail/r-help/2007-October/143567.html
o Added a CITATION file.
o Added a new "axis.text" setting.
o Added the option to scale data inside panel.3dscatter() and panel.3dwire() rather than assuming ther are already scaled. This may be helpful for use in user-written panel functions, with (additional) data specified in the original scale.
o 'varnames' can now be expressions in splom()/parallel().
o Added support for 'xlab.top' and 'ylab.right' arguments.
o Improved axis labelling in splom(), including support for date-time data.
o panel.pairs() now passes arguments i and j to (sub)panel and diag.panel functions.
o Default prepanel functions are now user-settable through lattice.options()
o par.[main|sub|xlab|ylab].text parameter settings are more powerful.
o Added support for 'just' component in draw.key() to allow justification of legend placement.
o Graphical arguments in panel.superpose can now be lists.
o Added support for raster colorkeys.
o Added new 'height' component for keys.
o Improved vectorization of graphical parameters in panel.bwplot.
o Expanded trellis.grobname() and used it to provide a name for all grobs.
o New panel.spline() function.
o More realistic check for equispaced grid in panel.levelplot.raster().
o Improved partial matching of component names in 'key' and 'scales'.
o xyplot.ts() now allows graphical parameters to be given as vectors (inside a list) for each series. Passes lists to panel.superpose.
o panel.axis() now does NOT draw tick marks if 'ticks = FALSE'.
o Hosting of the upstream sources has moved to R-forge. This allows, among other things, the use of the R-forge issue tracker.
o New xyplot.ts method, merging versions previously available in latticeExtra and zoo (thanks to the efforts of Felix Andrews)
o An argument 'group.value', containing the level of the group, is now passed by panel.superpose to the 'panel.groups' function
o Specifying 'auto.key' as a list now produces a legend even in the absence of 'groups', provided a 'text' component has been included
o The 'layout' argument now accepts NA for number of columns or rows.
o Scale limits 'xlim' & 'ylim' can have one NA to fix only one side.
o Date and POSIXt scales now use new methods to calculate axis ticks, and now respond to the 'tick.number' component of 'scales'.
o 'panel.qqmath' gains an argument 'tails.n' for exact data on tails.
o New function simpleTheme() for creating nested lists without specifying the nesting structure (which is guessed)
o Support for lattice.option(print.function) which is the function actually used when print.trellis() is called
o New argument 'box.width' wherever 'box.ratio' is available (e.g., panel.bwplot, panel.barchart, etc.), to specify absolute thickness (of boxes, bars, etc.)
o New panel.refline() function, same as panel.abline(), but with default parameters from the "reference.line" settings.
o parallel() has a new 'horizontal.axis' argument; when FALSE, the axes are vertical and are stacked side by side.
o densityplot() now supports weights.
o dotplot.table() etc. allow change of orientation (horizontal=FALSE).
o New function panel.identify.cloud() to interactively label three-dimensional scatterplots.
o Added support for notches in panel.bwplot (based on patch from Mike Kay)
o New panel function panel.smoothScatter (relocated from Bioconductor package geneplotter)
o Added German translations (contributed by Chris Leick)
o reordered documentation to make PDF manual more readable
o Make translations available (they were never actually installed before)
o 'x' in dotplot(~x, data) etc now gets names(x) set to rownames(data). Update: this feature has now been removed, as the resulting behaviour is undesirable for bwplot()
o the 'call' component of a "trellis" object is set to a better value than before (at least for the methods in lattice). One consequence is that update.default() now works for cases in which update.trellis() doesn't (i.e. those where data packets need to change)
o barchart.table now has an 'horizontal' argument
o levelplot.matrix() now allows specification of column labels or positions through arguments 'row.values' and 'column.values'
o width calculation for rectangles changed for levelplot() when 'x', 'y' are factors; they are set to 1, rather than trying to accomodate unequally spaced 'x' and 'y' values. This is important when there are empty levels
o dimnames() of a "trellis" object is now settable (this allows changing names and levels of conditioning variables)
o labels ('xlab', 'main', etc) can now be character vectors. In their list form, they support more graphical parameters as well as finer positioning (justification, rotation, etc.)
o 'strip.left' gets called with 'horizontal = FALSE', so 'strip.left = strip.default' now works as expected
(Some of these are also available in updated 0.14 versions)
o Default panel functions are now settable options
o Limits of a parallel coordinates plot can now be controlled via functions
o New 'panel.aspect' argument for cloud and wireframe
o Better support for factors in cloud and wireframe
o More flexible placement of legends with x, y and corner. In particular, corner can have fractional values, and (x, y) can refer to a position w.r.t. two potential bounding boxes depending on lattice.getOption("legend.bbox") ('full', meaning full plot region, or 'panel', meaning the subregion containing panels and strips. The default is 'panel', which is a change in behaiour)
o trellis.focus() now allows choosing panels interactively.
o New interaction functions panel.identify.qqmath() and panel.brush.splom()
o There is now an error handling mechanism for panel functions. By default, errors in panel functions no longer stop execution. See ?print.trellis for details.
o non-numeric data no longer cause warnings in bwplot
o the default padding between components has been changed to 0.5 "chars"
o support for custom function that determines packet-panel correspondence. This could be used to fill panels vertically rather than horizontally, or to split layout over two or more pages, etc. (see ?packet.panel.default)
o support for customizable functions for axis drawing and tick/label determination
o various accessor functions available to panel, strip, axis (etc) functions, e.g. panel.number() and packet.number()
o arguments to lattice.options and print.trellis arguments can now be attached to trellis objects (as parameter settings already could) through high level arguments 'lattice.options' and 'plot.args'
o llines, lpoints and ltext are now generic functions
o The high level 'key' argument can now have an argument called 'reverse.rows' to reverse the order of rows. This applies to 'draw.key', 'auto.key' and 'simpleKey' as well.
o extended interpretation of 'breaks' in histogram()
o matrix methods for 'splom' and 'parallel' (whose absence was an oversight)
o support of 'alpha' argument in labels and legends, which were previously missing for no good reason
o panel.grid() now allows 'h' and 'v' to have negative values other than -1, in which case '-h' and '-v' will be used as the 'n' argument to pretty() when determining line locations
o panel function is no longer given arguments panel.number and packet.number (see above for alternatives)
o panel.identify() now has a more useful return value (selected subscripts)
o trellis.panelArgs() without any arguments should return meaningful results while a "trellis" object is being printed, and thus should be usable inside panel or axis functions.
o For formulae of the form y1 + y2 ~ x1 + x2 + x3, the order of levels of the artificially created grouping variable is now more 'intuitive'
o high level generics like 'xyplot' now have both 'x' and 'data' as arguments. The only implication for S3 methods is that they will have to include the 'data' argument even if they are unused (as they should be when 'x' is not a formula). The reason for doing this is to encourage S4 methods using multiple dispatch where 'x' is a formula and 'data' is some other data source.
o R messages are now translatable.
o French translations courtesy of Philippe Grosjean.
o instead of ignoring it as before, 'panel.xyplot' and 'panel.densityplot' now deal with a 'groups' argument appropriately by calling 'panel.superpose'. Consequently, the default of 'panel' in 'xyplot' etc does not need to be conditional on 'groups'.
o added 'lineheight' as a graphical parameter where appropriate.
o added a 'grid.pars' setting for arbitrary grid parameters to be set initially via gpar().
o For a shingle 'x', 'as.character(levels(x))' creates meaningful labels.
o Shingle levels can now be printed by strip.default.
o The strip function, like the panel function, is now passed arguments 'packet.number' and 'panel.number' (although the default strip function makes no use of it).
o 'panel.superpose' has new argument to make it bahave like in S-PLUS (interpretation of 'type'). This makes 'panel.superpose.2' unnecessary, although it's still available.
o Added wrappers lrect, lpolygon (and panel.rect, panel.polygon)
o evaluation scope: standard functions with a formula based interface ('lm' etc) look for variables in the formula (that are not found in 'data') in the environment of the formula. This was done inconsistently for lattice functions, which has been fixed.
o 'summary.trellis' is now more informative
o calls with explicit 'formula=' no longer work (used to give a warning before)
o The 'bar.fill' and 'superpose.fill' settings have been replaced with 'plot.polygon' and 'superpose.polygon' respectively, which are more consistent with other names.
o Default of 'data' changed from 'parent.frame()' to NULL. This has to do with reasonable non-standard evaluation rules, and probably needs some more thought.
o Default Trellis settings (a.k.a. theme) changed. See ?trellis.device for details
o ltext now supports more 'adj' values
o scales$y$alternating now counts row numbers from top if as.table = TRUE
o miscellaneous improvements in strip.default
o change panel.qq so that most work gets done there
o panel.bwplot has a new 'stats' argument, which is a function used to calculate the statistics in the box and whisker plot. Defaults to boxplot.stats, which was the hard-coded value earlier.
o panel.bwplot has been re-implemented. Faster, avoids direct grid calls
o panel.densityplot now allows more flexible specifications of 'plot.points', specifically, points can be jittered (the new default) or indicated by a `rug'.
o (more) changes in NA-handling.
o panel.superpose handles type='g' itself so that the grid doesn't get repeated for every group.
o All high level functions are now generic. This change should be mostly transparent, but there may be some unforeseen side-effects. S3 generics and methods are used (this may change at some point, but not in the near future). In particular, usage where the first argument is not actually a formula has now been formalized and is handled via method dispatch rather than the clumsy hacks in place earlier.
o The first argument of high level lattice functions has been renamed from 'formula' to 'x'. This is related to the fact that these functions are now generic, and is intended to avoid long-term confusion. The first argument is usually not named, so this should not cause many problems. If the name 'formula' is explicitly supplied, it will be used with a warning (as long as there is no argument named 'x') for now, but not in future versions of lattice.
o aspect='xy' is now allowed when relation='free'
o A new function make.groups (present in S-PLUS) has been added.
o there's now panel.rect and lrect (similar to the base function rect)
o print.trellis has a 'draw.in' argument that can be used to specify a grid viewport to draw the plot in.
o strips can now be drawn on the left (as well as top) of a panel. This is useful for short wide panels, e.g. time series.
o 'Date' objects are recognized and axis labels formatted accordingly (not heavily tested)
o qqmath has been considerably revamped, primarily to allow grouped displays (the older implementation would not have allowed that even with a custom panel function). In particular, the (pre)panel function(s) now get the raw data as opposed to already computed quantiles. Some old code may stop working.
o as a consequence of the above, panel.qqmath, panel.qqmathline etc have been rewritten and have different argument lists
o tmd has been rewritten (mostly to deal with qqmath objects), but this shouldn't be user-visible.
o densityplot defaults to showing points with random jitter.
o arguments panel.number and panel.counter, passed to panel functions that have those (or the ...) argument(s) have been renamed to 'packet.number' and 'panel.number', which are more in line with standard Trellis jargon.
o identification of when 'type' should default to "density" was buggy (inapprpriate rounding)
o panel.superpose.2 (which replicates behaviour of panel.superpose in S-PLUS) revamped, with new features to boot.
o panel.identify improved
o larrows improved, slightly different features.
o [xyz]lab in cloud / wireframe can now be grobs, and honors a 'rot' component for rotation (e.g., zlab = list(rot = 90))
o some finer controls added to parallel (actually panel.parallel)
o trellis.last.object(...) now behaves like update(trellis.last.object(), ...))
o "trellis" objects now have a plot method that's essentially an alias to the print method
o new function 'current.panel.limits' to retrieve native scales of current panel (only in later versions)
o behaviour of auto.key = TRUE now function specific
o auto.key list now allows a 'text' component
o defaults of several standard arguments now taken from lattice.options()
o type='g' now calls panel.grid(h = -1, v = -1) rather thanjust panel.grid()
o NA-handling (may have undesirable effects)
o several minor fixes
o relation="free" and "sliced" now work for factors (at least, as well as can be expected)
o the code that constructs the layout of a lattice plot (in the print method for trellis objects) has been completely rewritten. This is mostly transparent to the user, but as a side effect, it is now possible to control the details of the layout (things like the amount of padding around the plot, the gap between tick marks and labels) via the trellis settings "layout.heights" and "layout.widths".
o col.regions and colorkey in levelplot and wireframe now honour settings in effect when the object is printed, and not when the object was created.
o xlab, ylab, main and sub can now be grobs
o datasets get separate documentation, contributed by Kevin Wright
o lattice.options(), similar to options(), to control various aspects of lattice plots. This is mostly for easier code maintainance, but can be useful for the user too.
o API now supports alpha-transparency (actual support is device dependent) where appropriate (some cases might have been missed, and reports of omissions would be appreciated).
o API for interacting with and enhancing Trellis plots AFTER they are drawn, based on grid functions seekViewport, grid.locator, etc. See ?trellis.focus
o aspect="iso" for `isometric' x- and y-axes.
o new 'default.scales' argument to high level functions, useful when writing wrappers
o convenience function 'strip.custom' to create strip functions from strip.default just by overriding one or more arguments
o type="H" in lplot.xy (for horizontal line). New argument 'horizontal' for panel.xyplot, which affects what happens for various 'type'-s.
o type="g" in panel.xyplot, which draws a reference grid
o the print method now (optionally) saves the (last) object printed in a non-visible environment. This allows retrieval of the last printed object for 'update'-ing, and more importantly, to retrieve panel specific data for use while interacting with and enhancing plots after they are printed
o a summary method for trellis objects (currently pretty basic)
o lset has been deprecated, and trellis.par.set has been enhanced with equivalent usage
o the strip function now gets the whole strip area to work with, and is responsible for using it appropriately. strip.default has been updated accordingly
o choice of color for grouped barcharts now taken from a new setting parameter 'superpose.fill' and not 'regions' as previously
o arguments to panel.levelplot has changed (this is related to how default colors are obtained, as described above).
o axes now drawn on last panel even if it doesn't fall on the border of the layout
o many other miscellaneous fixes, see SvnLog for some details
o Axis labelling code has been rewritten to internally use S3 method dispatch, with (unexported) methods for numeric (default), character (for factors), POSIXct and date. More methods can be considered on request. reversed limits are now allowed.
o contourplot can now handle missing rows in the data frame (equivalent to NA's in z). contourplot now uses contourLines().
o cloud and wireframe now use better 3-D projection calculations, and are generally much better than before. wireframe is much faster, and has a better shading algorithm. It can also handle NA's and missing rows.
o splom (specifically panel.pairs) has more functionality, including the option of using different panel functions below and above the diagonal, user defined diagonal panels, and a table-like layout (similar to pairs)
o font specifications now allow for fontface and fontfamily
o much improved update method for trellis objects
o setting auto.key = TRUE now computes key at printing time, honouring any changes in trellis settings
o arbitrary reordering of conditioning variables, as well as of levels within a conditioning variable. This works in the update method (as well as high-level plots), making it easy to examine parts of a multipanel trellis display and view it in different conditioning orders.
o extended key functionality (via the legend argument) that allows multiple legends and the use of arbitrary grid objects as keys
o option to NOT drop unused factor levels when subsetting, by setting drop.unused.levels = FALSE or drop.unused.levels = list(cond = FALSE, data = FALSE) in high-level functions like xyplot.
o Ability to attach settings to a trellis object (rather than changing the global settings), via argument par.settings in high level calls.
o Wireframe can now draw parametrized 3-D surfaces like spheres (generally of the form f(u,v) = (x(u,v), y(u,v), z(u,v)), for (u,v) in the square [0,1] x [0,1]).
o Functionality similar to locator() (possible due to recently added features of grid). All panels should have predictable viewport names, which can be used in seekViewport() to grab a particular viewport. grid.locator() can subsequently be used to locate points in the native coordinate system of that panel.
o allow.multiple now defaults to TRUE (whenever it makes sense), since '+' in a formula is interpreted differently than S-PLUS anyway. As in model formulae, I(x+y) works as expected.
o default behaviour of qq and qqmath changed (from S-PLUS behaviour) to match corresponding base functions qqplot and qqnorm
o Fixed important bug concerning interaction of subscripts and subsets
o lots of other fixes, mostly obscure
o Major change is the addition of a NAMESPACE. grid is now not 'require()-d', but imported only. To use grid functions directly in lattice calls (which is a very reasonable thing to do), one needs to explicitly call library(grid).
o contourplot() has improved when data has NA's. Still doesn't work when the NA rows are completely omitted (in other words, the full "matrix" has to be specified, even the entries with NA).
o Clipping can now be turned off in panels and strips via the trellis.par.get("clip") setting.
See the Changelog for other minor changes.
o The handling of Grouped displays has been made more consistent (and different from S-Plus). Whenever a groups= argument is specified, it is assumed that the user wants a grouped display and an attempt is made to honour this whenever appropriate (this ultimately depends on the panel function). A non-trivial addition to the list of functions that support this is barchart.
o Specification of legend (key) has been made slightly easier in the most common cases. The key is used most often in conjunction with the groups argument, and using the global trellis settings. The simpleKey function (and the auto.key argument to high level functions) uses the global settings to create a key with a not very flexible but simple interface.
o Handling of the formula argument has been extended to allow multiple variables on either side of the formula (with allow.multiple = TRUE), e.g. xyplot(y1 + y2 ~ x, data, allow.m = TRUE). These are treated as grouped displays.
o Some components of scales, namely tck, rot and cex, can now be length 2 vectors, controlling left/bottom and right/top separately.
o Some more functions (not all) now handle factors in the formula correctly (i.e., coerce them to numeric when factors are not appropriate, but use levels of the factor for labelling).
o panel functions: In earlier versions, panel functions and prepanel functions were guaranteed to be passed numeric vectors as x,y (and z) arguments. This is no longer true. All panel functions are now expected to handle other possibilities. This has been done in all the predefined panel functions in lattice (but not in llines, lpoints, etc.). In practice, the only changes required are (unless I have overlooked something) to add calls like
x <- as.numeric(x) y <- as.numeric(y)
at the beginning. prepanel functions can now return, as their xlim or ylim components, either a numeric vector of length 2 (possibly a DateTime object), or a character vector. The latter implies that the elements of this vector should be the respective axis labels, associated with tick marks at 1:length_of_this_vector.
o high-level functions: The default panel functions of high level functions can now be different, depending on whether a groups argument was passed. In practice, this now happens for xyplot, splom and densityplot. (densityplot has an additional high-level argument specifically for this, called panel.groups, which is passed to the panel function.) This is a convenience feature, (and is inconsistent with S-Plus) in that it presumes that if the user has specified a groups argument, she wants it to be used, where appropriate.
o scales: In anticipation of future use (in nlme, for example), the at and labels components of scales can now be a list. Each element corresponds to a panel. This is thoroughly untested and not guaranteed to work.
There are also some other API changes associated with cloud and wireframe, discussed below.
o Mathematical Annotation; Following changes in grid 0.7, lattice now supports latex-style labelling using expressions. These can be used in almost all sensible places (an exception being in colorkey axis labels in levelplot/contourplot, and this is not expected to change).
o Date-Time Labelling: Axis labelling procedures did not recognize DateTime objects in earlier versions. This has been fixed. The routine currently used is a hack of axis.POSIXt (without the format option), but will hopefully improve in future.
o 3-D functions:
The 3-D functions cloud and wireframe have been greatly improved in terms of extensibility. The code is much cleaner, and writing new panel functions are much simpler. Earlier versions had a problem with the default placement of the labels (x/y/z-lab) and scales (arrows/ticks), which has been fixed. [The only major problem that still remains is when, in a perspective plot, the projection of the distant face is fully contained inside the projection of the near face.]
Earlier wireframe code used an unnecessarily large amount of memory. This has been fixed, although speed is still not good (fixes are in the planing stage, and would involve changes in grid). drape=TRUE used to give wrong coloring, which is now fixed.
The 'group' argument now works with wireframe, resulting in multiple surfaces. This is mostly satisfactory, but is not sophisticated enough to render intersecting surfaces properly (might be approximated by a fine enough grid).
There are also some rudimentary lighting options, which can render the surface as being illuminated from a light source. No shadows. (Try shade=TRUE in wireframe.)
Although these changes go a long way towards stabilizing cloud/wireframe, some further changes, especially in how the panel function handles the groups argument, are expected in the future.
o Handling of NA values are often inconsistent and buggy. Some of these are not easily fixable (particularly one in contourplot), but some are, so bug reports on this are still welcome.
o Fonts specified in the new R font specification may not work yet.
o Biggest change in the way settings are handled. Settings are now stored in a global list called lattice.theme, and is truly device-specific (i.e., settings for more than one device can be used concurrently). Improved theme management via lset and show.settings. Changed defaults for color postscript/pdf.
o bwplot and friends which had to have the grouping factor/shingle on the y-axis, can now have it on the x-axis as well. Far from perfect, though, since long labels can overlap with default settings.
o panel.superpose now accepts an additional argument called panel.groups (by default panel.xyplot), which is the panel function actually called for each subset of the data determined by groups. Avoids having to write something as big as panel.superpose for natural generalizations like interaction plots. (Related new panel function: panel.linejoin)
o colorkey in levelplot on all sides. Rendering of large key's much much faster (using grid.place suggested by Paul)
o Other minor changes (doc, more arguments etc)
o Following changes in grid, calls to base R graphics and lattice functions can now be mixed.
Some of the implementation details have changed a lot. This might cause some old code to fail, though no such instances are known.
No significant new features have been added, but there are several bugfixes (notably in levelplot). The important changes are:
o documentation restructured. There is no topic called `trellis.args' any more. The detailed description of the arguments common to all high level trellis functions can be found under help(xyplot)
o once trellis.device() is called, Lattice graphics and base R graphics should mix more or less seamlessly. There is an optional argument in trellis.device() that can deal with the first blank page problem, with certain restrictions.
o a (as yet very small) demo, called by demo("lattice")
o Clipping: whatever is drawn by the panel function is now clipped to inside the panel region. Strip texts are clipped to inside the strips.
o Axis tick labels by default do not overlap, some tick marks are left unlabelled if necessary.
o The argument list for strip.default changed to be like S
o levels() and nlevels() give sensible answers for shingles. new print methods for shingles and levels of shingles
o colorkey (currently used only in levelplot) can now be placed to the left, top or bottom as well
o new ``lines'' component in the par.strip.text argument that can be used to change the height of strips
o xlab, main etc can be double height strings (containing "\n"-s), the spaces allocated for these would be automatically adjusted
o strip.default now has style=5
o new panel.superpose.2 (suggested by Neil Klepeis)
o the default colour settings sometimes seem too light on a white background. To deal with this, there is a new setting with some darker colours that can be set by calling lset(theme = "white.bg"). see ?lset for details. This is currently in a proof-of-concept stage (the colors in "white.bg" were chosen just because I liked their names), and suggestions for better color schemes would be most welcome.
o show.settings() added
The overall internal structure of the lattice library has changed considerably in verion 0.3, in particular making it far more readable and debuggable. However, this also means that some code which had worked with the earlier version might now fail. (This is just a discalimer, there are no known instances.)
o (Almost) full support for the `key' argument for drawing legends
o Support for log scales
o levelplot (but no contourplot. In particular, the contour = T option in levelplot does not work)
o tmd now works on the output from qq
o panel function names can now be quoted strings
o scales and its x and y components can now be just a character string like "free" or "sliced", i.e., the relation tag can be omitted.
o extension to the `type' argument in panel.xyplot and panel.superpose to allow stair-like and histogram-like plots (type="s" and "h" in plot), as well as loess smooths (using the loess.smooth function in the modreg package). Also, more than one of these options can now be used concurrently. This allows, for example, a grouped plot where a grouping variable can be used to fit separate loess curves along with the scatter for each group. See example(xyplot)
o wrappers around grid functions with API-s of traditional graphics functions to help port existing S-Plus Trellis code. See below for details.
o changes in print.trellis to allow mixing of Lattice and usual R graphics. See below for details.
One of the basic problems in porting existing Trellis code to R is the unusability of the base R functions like lines and points inside panel functions. To help make the changes more transparently, lattice now includes several wrappers around grid functions that provide an API similar to the corresponding base R functions. The list currently includes lpoints, llines, ltext and lsegments [update: larrows].
Grid graphics normally do not mix with usual R graphics. However, end-users typically might want to use lattice functions concurrently with traditional R graphics. To allow this without intermittent calls to grid.stop() and grid.start(), print.trellis (which ultimately does all the plotting in lattice) now tries to preserve the state of the device on which it plots. By default, library(lattice) opens a device in grid enabled mode. It can be reverted to non grid mode by grid.stop(). Subsequently, both Lattice functions and traditional graphics functions can be used. Devices opened by trellis.device() start in non-grid mode, unless grid.start() is called.
o contourplot, wireframe, cloud (partially implemented) and of course, piechart
o Some components of scale (I haven't found a full list, so can't say exactly which are missing)
o axis labels badly implemented, no checking for overlaps.
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