gss (version 2.2-8)

LakeAcidity: Water Acidity in Lakes

Description

Data extracted from the Eastern Lake Survey of 1984 conducted by the United States Environmental Protection Agency, concerning 112 lakes in the Blue Ridge.

Usage

data(LakeAcidity)

Format

A data frame containing 112 observations on the following variables.

ph	Surface ph.
cal	Calcium concentration.
lat	Latitude.
lon	Longitude.
geog	Geographic location, derived from lat and lon

Details

geog was generated from lat and lon using the code given in the Example section.

References

Gu, C. and Wahba, G. (1993), Semiparametric analysis of variance with tensor product thin plate splines. Journal of the Royal Statistical Society Ser. B, 55, 353--368.

Examples

## Converting latitude and longitude to x-y coordinates
if (FALSE) ltln2xy <- function(latlon,latlon0) {
  lat <- latlon[,1]*pi/180; lon <- latlon[,2]*pi/180
  lt0 <- latlon0[1]*pi/180; ln0 <- latlon0[2]*pi/180
  x <- cos(lt0)*sin(lon-ln0); y <- sin(lat-lt0)
  cbind(x,y)
}
data(LakeAcidity)
latlon <- as.matrix(LakeAcidity[,c("lat","lon")])
m.lat <- (min(latlon[,1])+max(latlon[,1]))/2
m.lon <- (min(latlon[,2])+max(latlon[,2]))/2
ltln2xy(latlon,c(m.lat,m.lon))
## Clean up
rm(ltln2xy,LakeAcidity,latlon,m.lat,m.lon)