add text for each cell of a 2D matrix plot in R (plotrix and/or ggplot2)

Question

A colored 2D matrix plot was created using the following codes:

library(plotrix)
testdf = data.frame(c(0,1,1),c(1,1,2),c(1,2,2))
color2D.matplot(testdf, 
                show.values = FALSE,
                axes = FALSE,
                xlab = "",
                ylab = "",
                vcex = 2,
                vcol = "black",
                extremes = c("red", "yellow", "green"))

However, this function can only show the numerical values within each cell, but what I want is some pre-specified texts (which can be provided from another data frame) added in each cell, like the screenshot below:

Is there a way in plotrix or some other R packages (e.g. ggplot2) that can make it? Thanks.

from [this](https://stackoverflow.com/questions/27406508/r-axis-label-in-image/27407719#27407719); `v <- c("A","C","B", "C", "CD","E", "B","C","D"); e <- expand.grid(seq(0.5,2.5, length=3), seq(2.5, 0.5, length=3)); text(e, labels=v, cex=2)` — user20650, Jul 22 '21 at 19:51
**v in the comment above should, of course, have been `v <- c("A","AB","B", "C", "CD","E", "B","C","D")` i.e. added rowwise — user20650, Jul 23 '21 at 08:47

score 2 · Accepted Answer · answered Jul 22 '21 at 18:51

Here is a way using ggplot2.

library(reshape2)
library(ggplot2)

testdf = data.frame(x = c(0,1,1),y = c(1,1,2),z = c(1,2,2))

# Convert testdf dataframe to a matrix.
df <- as.matrix(testdf)
# Flip the matrix horizontally, and put into long format.
df<-df[c(3:1), ,drop = FALSE] %>% 
  melt()

# Create a new dataframe with the names for each tile.
testdf_names <- data.frame(x = c("A","C","B"),y = c("AB","CD","C"),z = c("B","E","D"))
#Then, do the same process as above by first putting into a matrix.
df_names <- as.matrix(testdf_names)
# Flip the matrix horizontally, and put into long format.
df_names<-df_names[c(3:1), ,drop = FALSE] %>% 
  melt() %>% 
  dplyr::rename(names = value)

# Join the dataframes together for plotting.
df_new <- df %>% 
  dplyr::group_by(Var1, Var2) %>% 
  dplyr::left_join(df_names)

# Plot.
ggplot(df_new, aes(x = Var2, y = Var1)) + 
  geom_tile(aes(fill=as.factor(value)), color = "black", size = 1) + 
  scale_fill_manual(values=c("red", "yellow", "green")) +
  theme_void() + 
  theme(legend.position="none") +
  geom_text(aes(label=names), size = 30)

*Note: It isn't necessary to convert to a matrix; it is just a preference.

add text for each cell of a 2D matrix plot in R (plotrix and/or ggplot2)

1 Answers1