### Exercise box16.1 12x12 array

field<-matrix(1:144,nrow=12,ncol=12,byrow=TRUE)
# field
rowgroups<-list(c(1:3),c(4:6),c(7:9),c(10:12))
# rowgroups
colgroups<-list(c(1:4),c(5:8),c(9:12))
# colgroups

toSample<-list(NULL)
remember_subplot<-list(NULL)
count<-0
for(i in 1:4){
for(j in 1:3){
count<-count+1
submatrix<-field[rowgroups[[i]],colgroups[[j]]]
toSample[[count]]<-as.numeric(sample(paste(submatrix),4))
if(count %% 2 != 0) remember_subplot[[count]]<-paste(submatrix) # to be used in the plot
}}
# toSample




## Make a pretty plot
palegrey<-as.numeric(unlist(remember_subplot)) # to differentially colour our subplots, odd versus even



plot(NULL,axes=FALSE,xlim=c(0,12),ylim=c(0,12),xlab="",ylab="")
a<-0
for(j in 11:0) {
for(i in 0:11) {
a<-a+1
if(a %in% palegrey) rect(i,j,i+1,j+1,col="grey60")
else
rect(i,j,i+1,j+1,col="grey20")
text(i+.5,j+.5,a)
if(a %in% selectcell) text(i+.5,j+.5,a,col="red")
}}