Abstract

This short note shows how to plot a field map from an agricultural experiment and why that may be useful.

R setup

library("knitr")
## Warning: package 'knitr' was built under R version 3.3.2
knitr::opts_chunk$set(fig.align="center", fig.width=6, fig.height=6)
options(width=90)

Example 1

First, a plot of the experimental design of the oats data from Yates (1935).

library(agridat)
## Warning: package 'agridat' was built under R version 3.3.2
library(desplot)
## 
## Attaching package: 'desplot'
## The following objects are masked from 'package:agridat':
## 
##     RedGrayBlue, desplot
data(yates.oats)
# Older versions of agridat used x/y here instead of col/row
if(is.element("x",names(yates.oats)))
   yates.oats <- transform(yates.oats, col=x, row=y)
desplot(block ~ col+row, yates.oats,
        col=nitro, text=gen, cex=1, out1=block,
        out2=gen, out2.gpar=list(col = "gray50", lwd = 1, lty = 1))

Example 2

This next example is from Ryder (1981). Fit an ordinary RCB model with fixed effects for block and genotype. Plot a heatmap of the residuals.

library(agridat)
library(desplot)
data(ryder.groundnut)
gnut <- ryder.groundnut
m1 <- lm(dry ~ block + gen, gnut) # Standard RCB model
gnut$res <- resid(m1)
desplot(res ~ col + row, gnut, text=gen, cex=1,
        main="ryder.groundnut residuals from RCB model")

Note the largest positive/negative residuals are adjacent to each other, perhaps caused by the original data values being swapped. Checking with experiment investigators (managers, data collectors, etc.) is recommended.

Session info

sessionInfo()
## R version 3.3.1 (2016-06-21)
## Platform: x86_64-w64-mingw32/x64 (64-bit)
## Running under: Windows 7 x64 (build 7601) Service Pack 1
## 
## locale:
## [1] LC_COLLATE=C                           LC_CTYPE=English_United States.1252   
## [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
## [5] LC_TIME=English_United States.1252    
## 
## attached base packages:
## [1] stats     graphics  grDevices utils     datasets  methods   base     
## 
## other attached packages:
## [1] desplot_1.1  agridat_1.12 knitr_1.15.1
## 
## loaded via a namespace (and not attached):
##  [1] Rcpp_0.12.8     lattice_0.20-34 digest_0.6.10   rprojroot_1.1   grid_3.3.1     
##  [6] plyr_1.8.4      backports_1.0.4 magrittr_1.5    evaluate_0.10   stringi_1.1.2  
## [11] reshape2_1.4.2  rmarkdown_1.2   tools_3.3.1     stringr_1.1.0   yaml_2.1.14    
## [16] htmltools_0.3.5

References

Ryder, K. 1981. “Field Plans: Why the Biometrician Finds Them Useful.” Experimental Agriculture 17: 243–56. doi:10.1017/S0014479700011601.

Yates, Frank. 1935. “Complex Experiments.” Journal of the Royal Statistical Society Suppl 2: 181–247. doi:10.2307/2983638.