addLabels function

Add Labels to an Existing Plot

Add the label column of data to the existing plot.

addLabels (data, xlim = NULL, ylim = NULL, polyProps = NULL,
           placement = "DATA", polys = NULL, rollup = 3,
           cex = NULL, col = NULL, font = NULL, ...)

Arguments

• data: EventData or PolyData to add (required).
• xlim: range of X-coordinates.
• ylim: range of Y-coordinates.
• polyProps: PolyData specifying which labels to plot and their properties. par parameters passed as direct arguments supersede these data.
• placement: one of "DATA", "CENTROID", "MEAN_RANGE", or "MEAN_XY".
• polys: PolySet to use for calculating label placement.
• rollup: level of detail at which to process polys, and it should match that in data. 1 = PIDs only, 2 = outer contours only, and 3 = no roll-up.
• cex: vector describing character expansion factors (cycled by EID or PID).
• col: vector describing colours (cycled by EID or PID).
• font: vector describing fonts (cycled by EID or PID).
• ...: additional par parameters for the text function.

Details

If data is EventData , it must minimally contain the columns EID, X, Y, and label. Since the EID column does not match a column in polys, set placement = "DATA". The function plots each label at its corresponding X/Y coordinate.

If data is PolyData , it must minimally contain the columns PID and label. If it also contains X and Y columns, set placement = "DATA" to plot labels at those coordinates. Otherwise, set placement to one of "CENTROID", "MEAN_RANGE", or "MEAN_XY". When placement != "DATA", supply a PolySet polys. Using this PolySet , the function calculates a centroid, mean range, or mean X/Y coordinate for each polygon, and then links those PolyData with data by PID/SID to determine label coordinates.

If data contains both PID and EID columns, the function assumes it is PolyData and ignores the EID

column.

For additional help on the arguments cex, col, and font, please see par.

Returns

EventData or PolyData with X and Y columns that can subsequently reproduce the labels on the plot. Modify this data frame to tweak label positions.

Author(s)

Nicholas M. Boers, Staff Software Engineer

Jobber, Edmonton AB

Last modified Rd: 2013-04-10

See Also

addPoints, calcCentroid, calcMidRange, calcSummary, EventData , plotPoints, PolyData .

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  #--- create sample PolyData to label Vancouver Island
  labelData <- data.frame(PID=33, label="Vancouver Island");
  #--- load data
  if (!is.null(version$language) && (version$language == "R"))
    data(nepacLL,envir=.PBSmapEnv)
  #--- plot the map
  plotMap(nepacLL,xlim=c(-129,-122.6),ylim=c(48,51.1),col="lemonchiffon")
  #--- add the labels
  addLabels(labelData,placement="CENTROID",polys=nepacLL,cex=1.2,col=2,font=2)
  par(oldpar)
})