I have the code below to generate the heatmap with annotation.

library(pheatmap)
# Generate some data
test = matrix(rnorm(200), 20, 10)
test[1:10, seq(1, 10, 2)] = test[1:10, seq(1, 10, 2)] + 3
test[11:20, seq(2, 10, 2)] = test[11:20, seq(2, 10, 2)] + 2
test[15:20, seq(2, 10, 2)] = test[15:20, seq(2, 10, 2)] + 4
colnames(test) = paste("Test", 1:10, sep = "")
rownames(test) = paste("Gene", 1:20, sep = "")
# Add annotation as described above, and change the name of annotation
annotation <- data.frame(Var1 = factor(1:10 %% 2 == 0, labels = c("Exp1", "Exp2")))
rownames(annotation) <- colnames(test) # check out the row names of annotation
pheatmap(test, annotation = annotation)

I'm wondering whether there is a way to add the labels in the annotation bar in R code. Thanks in advance.