Home/ Questions/Q 8920413
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T06:15:49+00:00

When I make an experimental design, I use ggplot to show the layout. Here’s

  • 0

When I make an experimental design, I use ggplot to show the layout. Here’s a simple example: 

df <- data.frame(Block=rep(1:2, each=18),
            Row=rep(1:9, 4),
            Col=rep(1:4, each=9),
            Treat=sample(c(1:6),replace=F))

Which I’ll plot like: 

df.p <- ggplot(df, aes(Row, Col)) + geom_tile(aes(fill=as.factor(Treat)))

to give:

design

Sometimes I have a structure within the design I would like to highlight by putting a box around it, for example a mainplot. In this case: 

df$Mainplot <- ceiling(df$Row/3) + 3*(ceiling(df$Col/2) - 1)

I then use geom_rect and some messy code that needs adjusting for each design to generate something like:

designwithmainplot

Question: How do I add the rectangles around the mainplots in a simple way? It seems like a simple enough problem, but I haven’t found an obvious way. I can map colour or some other aesthetic to mainplot, but I can’t seem to surround them with a box. Any pointers greatly appreciated.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Here is a possible solution where I create an auxiliary data.frame for plotting borders with geom_rect(). I’m not sure if this is as simple as you would like! I hope the code that computes the rectangle coordinates will be reusable/generalizable with just a bit of additional effort.

    library(ggplot2)

# Load example data.
df = data.frame(Block=rep(1:2, each=18),
            Row=rep(1:9, 4),
            Col=rep(1:4, each=9),
            Treat=sample(c(1:6),replace=F))
df$Mainplot = ceiling(df$Row/3) + 3*(ceiling(df$Col/2) - 1)

# Create an auxiliary data.frame for plotting borders.
group_dat = data.frame(Mainplot=sort(unique(df$Mainplot)),
                       xmin=0, xmax=0, ymin=0, ymax=0)
# Fill data.frame with appropriate values.
for(i in 1:nrow(group_dat)) {
    item = group_dat$Mainplot[i]
    tmp = df[df$Mainplot == item, ]
    group_dat[i, "xmin"] = min(tmp$Row) - 0.5
    group_dat[i, "xmax"] = max(tmp$Row) + 0.5
    group_dat[i, "ymin"] = min(tmp$Col) - 0.5
    group_dat[i, "ymax"] = max(tmp$Col) + 0.5
}


p2 = ggplot() + 
     geom_tile(data=df, aes(x=Row, y=Col, fill=factor(Treat)), 
               colour="grey30", size=0.35) +
     geom_rect(data=group_dat, aes(xmin=xmin, xmax=xmax, ymin=ymin, ymax=ymax),
               size=1.4, colour="grey30", fill=NA)

ggsave(filename="plot_2.png", plot=p2, height=3, width=6.5)

    enter image description here

    • 0