R function for manipulative field experiment design - Plant ecology - r

Question

I am a plant ecologist and I would like to design a field manipulative experiment. To achieve a good degree of randomisation in the disposition of plants inside experimental plots, I would like to use R (with which I'm familiar).
The picture is a schematisation of the design: in total there would be 6 plots, each containing 24 different plant species. In total I have 36 plant species, from which I would like to randomly sample 24 species per plot (with high variation between plots). Each species should be present in 4 out of the 6 plots but in different positions, twice along the border (in two of the warm colours) and twice in the core area (once per cold colour); in the picture I visually explain what I mean using 4 different species (A, B, C, D).
Could anyone suggest a way to do it or some insight to write the function?

Answer 1

I borrowed some insight from this thread and this thread. Basically, you make a circular matrix and shuffle groups.
coords <- list(c(1,1),c(1,2),c(2,1),c(3,1),
c(1,3),c(1,4),c(2,4),c(3,4),
c(2,2),c(3,2),c(2,3),c(3,3),
c(4,1),c(5,1),c(6,1),c(6,2),
c(4,2),c(5,2),c(4,3),c(5,3),
c(4,4),c(5,4),c(6,3),c(6,4))
Matrix <- matrix(c(LETTERS,0:9)[1:36][matrix(1:36,36+1,36+1,byrow=T)[c(1,36:2),1:36]],36,36)
PlotLayouts <- Matrix[(1:6*6),1:24][,unlist(lapply(split(1:24,rep(1:6,each=4)),sample,4))]
PlotLayouts <- split(PlotLayouts,sample(1:6,6))
Result <- lapply(PlotLayouts,function(Vector){
Layout <- matrix(NA,nrow=6,ncol=4)
for(i in 1:24){
Layout[coords[[i]][1],coords[[i]][2]] <- Vector[i]
}
Layout
})
#Species Counts
table(unlist(Result))
0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4
Result
$`1`
[,1] [,2] [,3] [,4]
[1,] "I" "H" "M" "L"
[2,] "K" "R" "S" "N"
[3,] "J" "P" "Q" "O"
[4,] "U" "Z" "0" "2"
[5,] "V" "Y" "X" "1"
[6,] "T" "W" "4" "3"
$`2`
[,1] [,2] [,3] [,4]
[1,] "0" "Z" "4" "3"
[2,] "2" "9" "A" "5"
[3,] "1" "7" "8" "6"
[4,] "C" "H" "I" "K"
[5,] "D" "G" "F" "J"
[6,] "B" "E" "M" "L"
...