findPolys: Find Polygons that Contain Events

In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

Find Polygons that Contain Events

Description

Find the polygons in a PolySet that contain events specified in EventData.

Usage

findPolys (events, polys, maxRows = 1e+05, includeBdry=NULL)

Arguments

events	EventData to use.
polys	PolySet to use.
maxRows	estimated maximum number of rows in the output LocationSet.
includeBdry	numeric: determines how points on boundaries are handled: if NULL then report all points on polygon boundaries (default behaviour); if 0 then exclude all points on polygon boundaries; if 1 then report only the first (lowest PID/SID) polygon boundary; if 2,...,n then report the last (highest PID/SID) polygon boundary.

Details

The resulting data frame, a LocationSet, contains the columns EID, PID, SID (if in polys), and Bdry, where an event (EID) occurs in a polygon (PID, SID) and SID does not correspond to an inner boundary. The Boolean variable Bdry indicates whether an event lies on a polygon's edge. Note that if an event lies properly outside of all the polygons, then a record with (EID, PID, SID) does not occur in the output. It may happen, however, that an event occurs in multiple polygons. Thus, the same EID can occur more than once in the output.

If an event happens to lie at the boundary intersection of two or more polygons then one EID will be associated with two or more polygons. A user can choose to manipulate this result by setting the argument includeBdry to a numeric value that constrains the association of a boundary event to 0 or 1 polygon (see argument description above).

Value

LocationSet that links events with polygons.

Author(s)

Nicholas M. Boers, Staff Software Engineer
Jobber, Edmonton AB
Last modified Rd: 2014-12-15

See Also

combineEvents, findCells, locateEvents, locatePolys, LocationSet, makeGrid.

Examples

local(envir=.PBSmapEnv,expr={
  oldpar = par(no.readonly=TRUE)
  #--- create some EventData: a column of points at X = 0.5
  events <- data.frame(EID=1:10, X=.5, Y=seq(0, 2, length=10))
  events <- as.EventData(events, projection=1)
  #--- create a PolySet: two squares with the second above the first
  polys <- data.frame(PID=c(rep(1, 4), rep(2, 4)), POS=c(1:4, 1:4),
    X=c(0, 1, 1, 0, 0, 1, 1, 0),
    Y=c(0, 0, 1, 1, 1, 1, 2, 2))
  polys <- as.PolySet(polys, projection=1)
  #--- show a picture
  plotPolys(polys, xlim=range(polys$X)+c(-0.1, 0.1),
    ylim=range(polys$Y)+c(-0.1, 0.1), projection=1);
  addPoints(events, col=2);
  #--- run findPolys and print the results
  print(findPolys(events, polys))
  par(oldpar)
})

PBSmapping documentation built on Sept. 30, 2024, 9:21 a.m.