ggheatmap - Create a heatmap in ggplot2

ggheatmap.R

library(dplyr)
library(reshape2)
library(ggplot2)
#' Create a heatmap in ggplot2
#'
#' @param data Data set
#' @param print.cors Default TRUE. Should the correlations be printed in each block of the heatmap?
#' @param reoder Default TRUE. Should the entries be re-ordered via clustering, similar to `heatmap`?
#' @param colors Default c("red", "white", "blue"). Vector of length three defining colors for correaltions (1, 0, -1).
#'
#' @import dplyr, reshape2, ggplot2
#' @return A gg object.
ggheatmap <- function(data, print.cors = TRUE, reorder = TRUE, colors = c("red", "white", "blue")) {
  stopifnot(all(colors %in% colors()))
  stopifnot(length(colors) == 3)
  
  newdata <- select_if(data, is.numeric)
  if (reorder) {
    newdata <- newdata[, unlist(as.dendrogram(hclust(dist(cor(newdata, use = "pair")))))]
  }
  newdata <- melt(cor(newdata, use = "pair"))
  
  out <- ggplot(newdata, aes(x = Var1, y = Var2, fill = value)) + 
    geom_tile() + 
    scale_fill_gradient2(low = colors[3], high = colors[1], mid = colors[2],
                         midpoint = 0, limit = c(-1, 1), name = "Correlation") + 
    theme(axis.text.x = element_text(angle = 45, hjust = 1, vjust = 1),
          axis.title.x = element_blank(),
          axis.title.y = element_blank())
  if (print.cors) {
    out <- out + geom_label(aes(label = round(value, 2))) 
  }
  out
}

ggheatmap(iris, colors = c("green", "white", "orange"))