groupByPch: Group multiple SVG paths corresponding to same plotting...

In duncantl/SVGAnnotation: Tools for post-processing SVG plots created in R

Description

Typically, there is one SVG <path> element for each observation displayed in a plotting region. However, there are 10 different plotting characters in R that are made up multiple line segments and so give rise to multiple <path> elements in the resulting SVG output. To work with these more easily and sanely, it is convenient to convert the multiple path objects into a single group object for each such "point" in the display. This function does precisely that.

Note that is very difficult for us in this package to be able to infer the plotting character for a point except for in the most trivial of cases. That is why we have made this function available so that those who have contextual knowledge of the plot can perform this regrouping.

We collect the nodes related to the same observation and put them into a new <g> node and replace these nodes with that in the orginal parent node. We also add both a pch attribute to the <g> node which identifies to which pch value the new <g> corresponds and the type = 'plot-point' attribute-value pair.

The number of line segments/path elements for each plotting character is available in the variable numPathElementsPerPCH.

Usage

groupByPch(nodes, pch)

Arguments

nodes	the set of nodes corresponding to the observations, including some <path> elements that correspond to the same observation.
pch	the vector of values specified via the pch command to generate the plot in R that corresponds to these nodes, i.e. there may be different commands and different pch vectors for different subplots.

Value

The main result is the reorganization of the nodes. The return value is an integer vector that provides the grouping of the original nodes. The names indicate the plotting character from which the original node came.

Author(s)

Duncan Temple Lang

See Also

getPlotRegionNodes

See http://www.omegahat.org/SVGAnnotation/pch.svg for an example of how we collapsed the plotting characters into groups. The code to create this is below.

Examples

pch = c(7, 8, 10)
pp = svgPlot(plot(1:10, pch = pch))

rr = getPlotRegionNodes(pp)[[1]]
xmlSize(rr)
pts = getPlotPoints(pp)
length(pts)

groupByPch(pts, pch)
xmlSize(rr)
# Note that pts is irrelevant now.
# We need to fetch it again
pts = getPlotPoints(pp)


###########


doc = svgPlot(plot(1:26, pch = 0:25, bg = c("red")))
rr = getPlotRegionNodes(doc)[[1]]

v = groupByPch(xmlChildren(rr), 0:25)

  # now how many are remaining?
xmlSize(rr)

  # size of all the nodes. 0's correspond to path elements.
xmlSApply(rr, xmlSize)
  # how many are in each of the g's
sapply(rr[names(rr) == "g"], xmlSize)

  # check the pch attribute
sapply(rr[names(rr) == "g"], xmlAttrs)

saveXML(doc, "pch.svg")


################

pch = c(8,0, 3)
doc = svgPlot(plot(1:10, pch = pch))

rr = getPlotRegionNodes(doc)[[1]]
pts = getPlotPoints(doc)

xmlSize(rr)

groupByPch(pts, pch)
xmlSize(rr)
xmlSApply(rr, xmlSize)
sapply(rr[names(rr) == "g"], xmlSize)
names(rr)

sapply(rr[names(rr) == "g"], xmlAttrs)
xmlSApply(rr, function(x) "type" %in% names(xmlAttrs(x)))

xmlSApply(rr, xmlGetAttr, "pch")

duncantl/SVGAnnotation documentation built on May 15, 2019, 5:57 p.m.