R ggplot2: add text to geom_tiles

Question

I need to show the results of a clustering. For demo, please see

library(ggplot2)
df = data.frame(cluster=c(1,1,2,2,2,3),states=c("AB","IN","UN","CH","LO","OK"))
p2<-ggplot(df,aes(x=1,y=states,fill=factor(cluster)))+
    geom_tile()+
    geom_text(aes(label=cluster))
p2

How can I

Put the tiles with the same clustering number together?
Show only 1 clustering number per cluster?

My code above is reproducible and I appreciate it if you just can tweak it a little. Thanks.

1. Can be solved by reordering the factor levels in `states`. — Axeman, Oct 13 '15 at 08:26

score 7 · Accepted Answer · answered Oct 13 '15 at 08:38

You can change order of factor levels according to cluster with function reorder().

df$states<-reorder(df$states,df$cluster)

Then using reordered data, make new dataframe where pos is calculated as mean position of states that are converted to numeric.

library(plyr)
df2<-ddply(df,.(cluster),summarise,pos=mean(as.numeric(states)))

Now use new dataframe for adding labels.

ggplot(df,aes(x=1,y=states,fill=factor(cluster)))+
      geom_tile()+
      geom_text(data=df2,aes(y=pos,label=cluster))

score 1 · Answer 2 · answered Oct 13 '15 at 08:50

Another way is to use scale_y_discrete to set the order of the tiles and use blank labels on geom_text to just have 1 label per tile.

This can do the trick:

ggplot(df,aes(x=1,y=states,fill=factor(cluster)))+
  geom_tile()+
  geom_text(aes(label=c('1', '', '', '', '2', '3')))+
  scale_y_discrete(limits=c("AB", "IN", "CH", "LO", "UN", "OK"))

Notice that the label won't be in the middle of an even number of elements in a cluster though. It will be in your chosen position.

R ggplot2: add text to geom_tiles

2 Answers2