interaction: Functions to Interact with Lattice Plots

Description

The classic Trellis paradigm is to plot the whole object at once, without the possibility of interacting with it afterwards. However, by keeping track of the grid viewports where the panels and strips are drawn, it is possible to go back to them afterwards and enhance them one panel at a time. These functions provide convenient interfaces to help in this. Note that these are still experimental and the exact details may change in future.

Usage

panel.identify(x, y = NULL,
               subscripts = seq_along(x),
               labels = subscripts, 
               n = length(x), offset = 0.5,
               threshold = 18, ## in points, roughly 0.25 inches
               panel.args = trellis.panelArgs(),
               ...)
panel.identify.qqmath(x, distribution, groups, subscripts, labels,
                      panel.args = trellis.panelArgs(),
                      ...)
panel.link.splom(threshold = 18, verbose = getOption("verbose"), ...)
panel.brush.splom(threshold = 18, verbose = getOption("verbose"), ...)
trellis.vpname(name = c("position", "split", "split.location", "toplevel",
               "panel", "strip", "strip.left", "legend",
               "main", "sub", "xlab", "ylab", "page"),
               column, row,
               side = c("left", "top", "right", "bottom", "inside"),
               clip.off = FALSE, prefix)
trellis.grobname(name, prefix)
trellis.focus(name, column, row, side, clip.off,
              highlight = interactive(), ...,
              guess = TRUE, verbose = getOption("verbose"))
trellis.switchFocus(name, side, clip.off, highlight, ...)
trellis.unfocus()
trellis.panelArgs(x, packet.number)

Arguments

x, y

variables defining the contents of the panel. In the case of trellis.panelArgs, a "trellis" object.

the number of points to identify by default (overridden by a right click)

subscripts

an optional vector of integer indices associated with each point. See details below.

labels

an optional vector of labels associated with each point. Defaults to subscripts

distribution, groups

typical panel arguments of panel.qqmath. These will usually be obtained from panel.args

offset

the labels are printed either below, above, to the left or to the right of the identified point, depending on the relative location of the mouse click. The offset specifies (in "char" units) how far from the identified point the l

threshold

threshold in grid's "points" units. Points further than these from the mouse click position are not considered

panel.args

list that contains components names x (and usually y), to be used if x is missing. Typically, when called after trellis.focus, this would appropriately be the arguments passed to that panel.

name

character string indicating which viewport or grob we are looking for. Although these do not necessarily provide access to all viewports and grobs created by a lattice plot, they cover most that users might find interesting.

trelli

column, row

integers, indicating position of the panel or strip that should be assigned focus in the Trellis layout. Rows are usually calculated from the bottom up, unless the plot was created with as.table=TRUE

guess

logical. If TRUE, and the display has only one panel, that panel will be automatically selected by a call to trellis.focus.

side

character string, relevant only for legends (i.e., when name="legend"), indicating their position. Partial specification is allowed, as long as it is unambiguous.

clip.off

logical, whether clipping should be off, relevant when name is "panel" or "strip". This is necessary if axes are to be drawn outside the panel or strip. Note that setting clip.off=FALSE doe

prefix

character string acting as a prefix, meant to distinguish otherwise equivalent viewports in different plots. This only becomes relevant when a particular page is occupied by more than one plot. Defaults to the value appropriate for the last <

highlight

logical, whether the viewport being assigned focus should be highlighted. For trellis.focus, the default is TRUE in interactive mode, and trellis.switchFocus by default preserves the setting currently ac

packet.number

integer, which panel to get data from. See packet.number for details on how this is calculated

verbose

whether details will be printed

...

For panel.identify.qqmath, extra parameters are passed on to panel.identify. For panel.identify, extra arguments are treated as graphical parameters and are used for labelling. For trellis.focus

`Value`

panel.identify returns an integer vector containing the
  subscripts of the identified points (see details above).  The
  equivalent of identify with pos=TRUE is not yet
  implemented, but can be considered for addition if requested.
  trellis.panelArgs returns a named list of arguments that were
  available to the panel function for the chosen panel.
  trellis.vpname and trellis.grobname return character
  strings.
  trellis.focus has a meaningful return value only if it has been
  used to focus on a panel interactively, in which case the return value
  is a list with components col and row giving the column
  and row positions respectively of the chosen panel, unless the choice
  was cancelled (by a right click), in which case the return value is
  NULL.  If click was outside a panel, both col and
  row are set to 0.

`concept`

interaction
augment

`Details`

panel.identify is similar to identify.  When
  called, it waits for the user to identify points (in the panel being
  drawn) via mouse clicks.  Clicks other than left-clicks terminate the
  procedure.  Although it is possible to call it as part of the panel
  function, it is more typical to use it to identify points after
  plotting the whole object, in which case a call to
  trellis.focus first is necessary.
  panel.link.splom is meant for use with splom,
  and requires a panel to be chosen using trellis.focus before it
  is called.  Clicking on a point causes that and the corresponding
  proections in other pairwise scatter plots to be highlighted.
  panel.brush.splom is a (misnamed) alias for
  panel.link.splom, retained for back-compatibility.
  panel.identify.qqmath is a specialized wrapper meant for use
  with the display produced by qqmath.
  
  One way in which panel.identify etc. are different from
  identify is in how it uses the subscripts
  argument.  In general, when one identifies points in a panel, one
  wants to identify the origin in the data frame used to produce the
  plot, and not within that particular panel.  This information is
  available to the panel function, but only in certain situations.  One
  way to ensure that subscripts is available is to specify
  subscripts = TRUE in the high level call such as xyplot.
  If subscripts is not explicitly specified in the call to
  panel.identify, but is available in panel.args, then
  those values will be used.  Otherwise, they default to
  seq_along(x).  In either case, the final return value will be
  the subscripts that were marked.
  The process of printing (plotting) a Trellis object builds up a grid
  layout with named viewports which can then be accessed to modify the
  plot further.  While full flexibility can only be obtained by using
  grid functions directly, a few lattice functions are available for the
  more common tasks.
  trellis.focus can be used to move to a particular panel or
  strip, identified by its position in the array of panels.  It can also
  be used to focus on the viewport corresponding to one of the labels or
  a legend, though such usage would be less useful.  The exact
  viewport is determined by the name along with the other
  arguments, not all of which are relevant for all names.  Note that
  when more than one object is plotted on a page, trellis.focus
  will always go to the plot that was created last.  For more
  flexibility, use grid functions directly (see note below).
  After a successful call to trellis.focus, the desired viewport
  (typically panel or strip area) will be made the current
  viewport (plotting area), which can then be enhanced by calls to
  standard lattice panel functions as well as grid functions.
  It is quite common to have the layout of panels chosen when a
  "trellis" object is drawn, and not before then.  Information on
  the layout (specifically, how many rows and columns, and which packet
  belongs in which position in this layout) is retained for the last
  "trellis" object plotted, and is available through
  trellis.currentLayout.
  trellis.unfocus unsets the focus, and makes the top level
  viewport the current viewport.
  trellis.switchFocus is a convenience function to switch from
  one viewport to another, while preserving the current row and
  column.  Although the rows and columns only make sense for
  panels and strips, they would be preserved even when the user switches
  to some other viewport (where row/column is irrelevant) and then
  switches back.
  
  Once a panel or strip is in focus, trellis.panelArgs can be
  used to retrieve the arguments that were available to the panel
  function at that position.  In this case, it can be called without
  arguments as
  trellis.panelArgs()
  This usage is also allowed when a "trellis" object is being
  printed, e.g. inside the panel functions or the axis function (but not
  inside the prepanel function).  trellis.panelArgs can also
  retrieve the panel arguments from any "trellis" object.  Note
  that for this usage, one needs to specify the packet.number (as
  described under the panel entry in xyplot) and
  not the position in the layout, because a layout determines the panel
  only after the object has been printed.
  It is usually not necessary to call trellis.vpname and
  trellis.grobname directly.  However, they can be useful in
  generating appropriate names in a portable way when using grid
  functions to interact with the plots directly, as described in the
  note below.

`See Also`

identify, Lattice,
  print.trellis, trellis.currentLayout,
  current.vpTree,
  viewports

`Examples`

Run this codexyplot(1:10 ~ 1:10)
trellis.focus("panel", 1, 1)
panel.identify()

xyplot(Petal.Length ~ Sepal.Length | Species, iris, layout = c(2, 2))
Sys.sleep(1)

trellis.focus("panel", 1, 1)
do.call("panel.lmline", trellis.panelArgs())
Sys.sleep(0.5)
trellis.unfocus()

trellis.focus("panel", 2, 1)
do.call("panel.lmline", trellis.panelArgs())
Sys.sleep(0.5)
trellis.unfocus()

trellis.focus("panel", 1, 2)
do.call("panel.lmline", trellis.panelArgs())
Sys.sleep(0.5)
trellis.unfocus()


## choosing loess smoothing parameter

p <- xyplot(dist ~ speed, cars)

panel.loessresid <-
    function(x = panel.args$x,
             y = panel.args$y,
             span,
             panel.args = trellis.panelArgs())
{
    fm <- loess(y ~ x, span = span)
    xgrid <- do.breaks(current.panel.limits()$xlim, 50)
    ygrid <- predict(fm, newdata = data.frame(x = xgrid))
    panel.lines(xgrid, ygrid)
    pred <- predict(fm)
    ## center residuals so that they fall inside panel
    resids <- y - pred + mean(y)
    fm.resid <- loess.smooth(x, resids, span = span)
    ##panel.points(x, resids, col = 1, pch = 4)
    panel.lines(fm.resid, col = 1)
}


spans <- c(0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8)
update(p, index.cond = list(rep(1, length(spans))))
panel.locs <- trellis.currentLayout()

i <- 1

for (row in 1:nrow(panel.locs))
    for (column in 1:ncol(panel.locs))
    if (panel.locs[row, column] > 0)
{
    trellis.focus("panel", row = row, column = column,
                  highlight = FALSE)
    panel.loessresid(span = spans[i])
    grid::grid.text(paste("span = ", spans[i]),
                    x = 0.25,
                    y = 0.75,
                    default.units = "npc")
    trellis.unfocus()
    i <- i + 1
}
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