# thinPolys: Thin a PolySet of Polygons In PBSmapping: Mapping Fisheries Data and Spatial Analysis Tools

## Description

Thin a PolySet, where each unique (`PID`, `SID`) describes a polygon.

## Usage

 `1` ```thinPolys (polys, tol = 1, filter = 3) ```

## Arguments

 `polys` PolySet to thin. `tol` tolerance (in kilometres when `proj` is `"LL"` and `"UTM"`; otherwise, same units as `polys`). `filter` minimum number of vertices per result polygon.

## Details

This function executes the Douglas-Peuker line simplification algorithm on each polygon within `polys`.

## Value

PolySet containing the thinned data. The function recalculates the `POS` values for each polygon.

## Author(s)

Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified `Rd: 2013-04-10`

## See Also

`thickenPolys`.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```local(envir=.PBSmapEnv,expr={ oldpar = par(no.readonly=TRUE) #--- load the data (if using R) if (!is.null(version\$language) && (version\$language=="R")) data(nepacLL,envir=.PBSmapEnv) #--- plot a thinned version of Vancouver Island (3 km tolerance) plotMap(thinPolys(nepacLL[nepacLL\$PID == 33, ], tol = 3)) #--- add the original Vancouver Island in a different line type to #--- emphasize the difference addPolys(nepacLL[nepacLL\$PID == 33, ], border=2, lty=8, density=0) par(oldpar) }) ```

PBSmapping documentation built on Jan. 15, 2021, 3:41 p.m.