wheat {spData}

Mercer and Hall wheat yield data

Description

Mercer and Hall wheat yield data, based on version in Cressie (1993), p. 455.

Usage

wheat

Format

The format of the object generated by running data(wheat) is a three column data frame made available by Hongfei Li. The example section shows how to convert this to the object used in demonstrating the aple function, and is a formal class 'SpatialPolygonsDataFrame' [package "sp"] with 5 slots; the data slot is a data frame with 500 observations on the following 6 variables.

• lat: local coordinates northings ordered north to south

• yield: Mercer and Hall wheat yield data

• r: rows south to north; levels in distance units of plot centres

• c: columns west to east; levels in distance units of plot centres

• lon: local coordinates eastings

• lat1: local coordinates northings ordered south to north

Note

The value of 4.03 was changed to 4.33 (wheat[71,]) 13 January 2014; thanks to Sandy Burden; cross-checked with http://www.itc.nl/personal/rossiter/teach/R/mhw.csv, which agrees.

Source

Cressie, N. A. C. (1993) Statistics for Spatial Data. Wiley, New York, p. 455.

References

Mercer, W. B. and Hall, A. D. (1911) The experimental error of field trials. Journal of Agricultural Science 4, 107-132.

Examples

if (requireNamespace("sp", quietly = TRUE)) {
library(sp)
data(wheat)
wheat$lat1 <- 69 - wheat$lat
wheat$r <- factor(wheat$lat1)
wheat$c <- factor(wheat$lon)
wheat_sp <- wheat
coordinates(wheat_sp) <- c("lon", "lat1")
wheat_spg <- wheat_sp

gridded(wheat_spg) <- TRUE
wheat_spl <- as(wheat_spg, "SpatialPolygons")
df <- as(wheat_spg, "data.frame")
row.names(df) <- sapply(slot(wheat_spl, "polygons"),
                        function(x) slot(x, "ID"))
wheat <- SpatialPolygonsDataFrame(wheat_spl, data=df)
}


if (requireNamespace("sf", quietly = TRUE)) {
  library(sf)
  wheat <- st_read(system.file("shapes/wheat.shp", package="spData"))
  plot(wheat)
}