wheat {spData} | R Documentation

## 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

    ## Not run:
    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)

    ## End(Not run)

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

[Package spData version 0.3.0 Index]