Wheat yields at Rothamsted in 1910 (Mercer and Hall Wheat Yield data)

Description:

These data were taken from the R package `spdep'. The Mercer and Hall yield data consist of wheat yields on a 20 by 25 lattice of plots which total to around 1 acre in area. Each of the 20 rows runs in the E-W direction and each of the 25 columns in the N-S direction. Authors have analysed the wheat-yield data using both lattice models (through specification of the inverse covariance matrix) and geostatistical models (through specification of the covariance matrix). More details on these data can be found in Cressie (1993) pp. 248--259, 454--456.

Format:

This is a three column csv file, the data in which was made available by Hongfei Li. There are 500 observations on the following 6 variables.

• lat: local coordinates northings ordered north to south

• lon: local coordinates eastings

• yield: Mercer and Hall wheat yield data.

Note:

• These are /local/ lat-lon coordinates.

• 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.

The following image can be generated as follows:

library(ggplot2)
wheat <- read.table("wheat.csv",sep=",",header=T)
g <- ggplot() + geom_tile(data=wheat,aes(lon,lat,fill=yield)) + coord_fixed() + scale_fill_gradient(low="light yellow",high="dark blue")
ggsave("wheat.jpg")

References:

Cressie, N. A. C. (1993) Statistics for Spatial Data. Wiley, New York, p. 455. Mercer, W. B. and Hall, A. D. (1911) The experimental error of field trials. Journal of Agricultural Science 4, 107-132.