Trim a Data Set To Map Boundaries

Description

Takes a subset of a data frame: returns rows with geolocations inside the boundaries determined by a map. If rectangle=FALSE, strict map boundaries are used. If rectangle=TRUE, a rectangular boundary is determined based on the range of X and Y coordinates for the map, along with an optional buffer.

Usage

trimdata(rdata, map, Xcol=2, Ycol=3, rectangle=F, buffer=0.05)

Arguments

Details

Various functions from the PBSmapping package and maptools package are used to convert map formats, check whether the map and data are aligned, and clip the grid. Without the PBSmapping package only rectangle=TRUE will work. Be sure to use fill=T when using the map function to produce maps for trimdata: maps produced using the default fill=F argument do not work properly with this function. If the map centroid is not in the range of the data and the PBSmapping package is available a warning message is printed; this might indicate differing projections but can occur naturally when the data were not sampled from the entire extent of the map or when map boundaries are concave.

Value

A subset of the rdata data frame containing only those rows with geolocations within the specified boundaries.

Author(s)

Veronica Vieira, Scott Bartell, and Robin Bliss

Send bug reports to sbartell@uci.edu.

See Also

predgrid, optspan, modgam, colormap.

Examples

# These examples require the "PBSmapping" and "maps" packages
if (require(maps) & require(PBSmapping)) {
data(beertweets)
dim(beertweets)

### Trim data to US base map, and plot them
basemap1 <- map("usa", fill=TRUE, col="transparent")	
dUS <- trimdata(beertweets, basemap1)	 				 
# Plot tweet locations (beer tweets in red)
points(dUS$longitude, dUS$latitude, col=dUS$beer+1, cex=0.5)		

### Trim data to Texas base map, and plot them
basemap2 <- map("state", regions="texas", fill=TRUE, col="transparent") 
dTX <- trimdata(beertweets, basemap2) 								
# Plot tweet locations (beer tweets in red)
points(dTX$longitude, dTX$latitude, col=dTX$beer+1, cex=0.5) 
}

Results

R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(MapGAM)
Loading required package: sp
Loading required package: gam
Loading required package: splines
Loading required package: foreach
Loaded gam 1.12

> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/MapGAM/trimdata.Rd_%03d_medium.png", width=480, height=480)
> ### Name: trimdata
> ### Title: Trim a Data Set To Map Boundaries
> ### Aliases: trimdata
> ### Keywords: misc
> 
> ### ** Examples
> 
> # These examples require the "PBSmapping" and "maps" packages
> if (require(maps) & require(PBSmapping)) {
+ data(beertweets)
+ dim(beertweets)
+ 
+ ### Trim data to US base map, and plot them
+ basemap1 <- map("usa", fill=TRUE, col="transparent")	
+ dUS <- trimdata(beertweets, basemap1)	 				 
+ # Plot tweet locations (beer tweets in red)
+ points(dUS$longitude, dUS$latitude, col=dUS$beer+1, cex=0.5)		
+ 
+ ### Trim data to Texas base map, and plot them
+ basemap2 <- map("state", regions="texas", fill=TRUE, col="transparent") 
+ dTX <- trimdata(beertweets, basemap2) 								
+ # Plot tweet locations (beer tweets in red)
+ points(dTX$longitude, dTX$latitude, col=dTX$beer+1, cex=0.5) 
+ }
Loading required package: maps

 # maps v3.1: updated 'world': all lakes moved to separate new #
 # 'lakes' database. Type '?world' or 'news(package="maps")'.  #


Loading required package: PBSmapping

-----------------------------------------------------------
PBS Mapping 2.69.76 -- Copyright (C) 2003-2016 Fisheries and Oceans Canada

PBS Mapping comes with ABSOLUTELY NO WARRANTY;
for details see the file COPYING.
This is free software, and you are welcome to redistribute
it under certain conditions, as outlined in the above file.

A complete user guide 'PBSmapping-UG.pdf' is located at 
/home/ddbj/local/lib64/R/library/PBSmapping/doc/PBSmapping-UG.pdf

Packaged on 2015-04-23
Pacific Biological Station, Nanaimo

All available PBS packages can be found at
http://code.google.com/p/pbs-software/

To see demos, type '.PBSfigs()'.
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