I've seen heatmaps with values made in various R graphics systems including lattice and base like this:
I tend to use ggplot2
a bit and would like to be able to make a heatmap with the corresponding cell values plotted. Here's the heat map and an attempt using geom_text
:
library(reshape2, ggplot2)
dat <- matrix(rnorm(100, 3, 1), ncol=10)
names(dat) <- paste("X", 1:10)
dat2 <- melt(dat, id.var = "X1")
p1 <- ggplot(dat2, aes(as.factor(Var1), Var2, group=Var2)) +
geom_tile(aes(fill = value)) +
scale_fill_gradient(low = "white", high = "red")
p1
#attempt
labs <- c(apply(round(dat[, -2], 1), 2, as.character))
p1 + geom_text(aes(label=labs), size=1)
Normally I can figure out the x and y values to pass but I don't know in this case since this info isn't stored in the data set. How can I place the text on the heatmap?
Key is to add a row identifier to the data and shape it "longer".
edit Dec 2022 to make code reproducible with R 4.2.2 / ggplot2 3.4.0 and reflect changes in tidyverse semantics
library(ggplot2)
library(tidyverse)
dat <- matrix(rnorm(100, 3, 1), ncol = 10)
## the matrix needs names
names(dat) <- paste("X", 1:10)
## convert to tibble, add row identifier, and shape "long"
dat2 <-
dat %>%
as_tibble() %>%
rownames_to_column("Var1") %>%
pivot_longer(-Var1, names_to = "Var2", values_to = "value") %>%
mutate(
Var1 = factor(Var1, levels = 1:10),
Var2 = factor(gsub("V", "", Var2), levels = 1:10)
)
#> Warning: The `x` argument of `as_tibble.matrix()` must have unique column names if
#> `.name_repair` is omitted as of tibble 2.0.0.
#> ℹ Using compatibility `.name_repair`.
ggplot(dat2, aes(Var1, Var2)) +
geom_tile(aes(fill = value)) +
geom_text(aes(label = round(value, 1))) +
scale_fill_gradient(low = "white", high = "red")
Created on 2022-12-31 with reprex v2.0.2