PBSmapping (version 2.73.4)

calcSummary: Apply Functions to Polygons in a PolySet

Description

Apply functions to polygons in a PolySet.

Usage

calcSummary (polys, rollup = 3, FUN, ...)

Value

PolyData with columns PID, SID (may be missing),

X, and Y. If FUN returns a vector of length greater than 1 (say n), names the columns X1, X2, ..., Xn and Y1, Y2, ..., Yn.

Arguments

polys

PolySet to use.

rollup

level of detail in the results; 1 = PIDs only, by removing the SID column, and then passing each PID into FUN, 2 = outer contours only, by making hole SIDs equal to their parent's SID, and then passing each (PID, SID) into FUN, and 3 = no roll-up.

FUN

the function to apply; it must accept a vector and return a vector or scalar.

...

optional arguments for FUN.

Author

Nicholas M. Boers, Staff Software Engineer
Jobber, Edmonton AB
Last modified Rd: 2013-04-10

Details

If rollup equals 1, the results contain an entry for each unique PID only. When it equals 2, they contain entries for outer contours only. Finally, setting it to 3 prevents roll-up, and they contain an entry for each unique (PID, SID).

See Also

calcArea, calcCentroid, calcConvexHull, calcLength, calcMidRange, combineEvents, findPolys, locateEvents, locatePolys, makeGrid, makeProps.

Examples

local(envir=.PBSmapEnv,expr={
  #--- load the data (if using R)
  if (!is.null(version$language) && (version$language=="R"))
    data(nepacLL,envir=.PBSmapEnv)
  #--- calculate and print the centroids for several polygons
  print(calcSummary(nepacLL[is.element(nepacLL$PID,c(33,39,47)),],
    rollup=3, FUN=mean))
})