Description Usage Arguments Details Value Author(s) See Also Examples

Find the grid cells in a PolySet that contain events specified in
EventData. Similar to `findPolys`

, except this
function requires a PolySet resulting from
`makeGrid`

. This restriction allows this function to
calculate the result with greater efficiency.

1 | ```
findCells (events, polys, includeBdry=NULL)
``` |

`events` |
EventData to use. |

`polys` |
PolySet to use. |

`includeBdry` |
numeric: determines how points on boundaries are handled: |

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`

). The Boolean (0,1) 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 (i.e., on two or
more boundaries). Thus, the same `EID`

can occur more than once
in the output.

If an event happens to lie at the boundary intersection of four (or two) grid cells
then one `EID`

will be associated with four (or two) grid cells. 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 grid cell (see argument description above).

LocationSet that links events with polygons.

Nicholas M. Boers, Associate Professor – Computer Science

MacEwan University, Edmonton AB

Last modified `Rd: 2014-12-15`

`findPolys`

,
`makeGrid`

,
`combineEvents`

,
`locateEvents`

,
`locatePolys`

,
LocationSet.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | ```
local(envir=.PBSmapEnv,expr={
oldpar = par(no.readonly=TRUE)
#--- create some EventData: points in a diagonal line
events <- data.frame(EID=1:11, X=seq(0, 2, length=11),
Y=seq(0, 2, length=11))
events <- as.EventData(events, projection=1);
#--- create a PolySet (a grid)
polys <- makeGrid (x=seq(0, 2, by=0.50), y=seq(0, 2, by=0.50), 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 findCells and print the results
fc <- findCells(events, polys)
fc <- fc[order(fc$EID, fc$PID, fc$SID), ]
fc$label <- paste(fc$PID, fc$SID, sep=", ")
print (fc)
#--- add labels to the graph
addLabels(as.PolyData(fc[!duplicated(paste(fc$PID,fc$SID)), ],
projection=1), placement="CENTROID",
polys=as.PolySet(polys, projection=1), col=4)
par(oldpar)
})
``` |

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