Circular Heatmap that looks like a donut

Question

I'm trying to create circular heatmap with ggplot2 so I can use a larger number of labels around the circumference of a circle. I'd like to have it look more like a donut with an empty hole in the middle but at the same time not losing any rows (they would need to be compressed).

Code for what I have is below.

library(reshape) library(ggplot2)  nba <- read.csv("http://datasets.flowingdata.com/ppg2008.csv")  nba$Name <- with(nba, reorder(Name, PTS)) nba.m <- melt(nba) nba.m <- ddply(nba.m, .(variable), transform, value = scale(value))   p = ggplot(nba.m, aes(Name,variable)) + geom_tile(aes(fill = value), colour = "white") +           scale_fill_gradient(low = "white", high = "steelblue")  p<-p+opts( panel.background=theme_blank(), axis.title.x=theme_blank(), axis.title.y=theme_blank(), panel.grid.major=theme_blank(), panel.grid.minor=theme_blank(),   axis.text.x=theme_blank(), axis.ticks=theme_blank() )   p = p + coord_polar()  plot(p)  

Answer 1

Here is a solution accomplished by (1) converting factor to numeric and adding an offset, (2) manually specifying y-limits and (3) manually setting y-axis breaks and labels:

library(reshape) library(ggplot2) # Using ggplot2 0.9.2.1  nba <- read.csv("http://datasets.flowingdata.com/ppg2008.csv") nba$Name <- with(nba, reorder(Name, PTS)) nba.m <- melt(nba) nba.m <- ddply(nba.m, .(variable), transform, value = scale(value))  # Convert the factor levels to numeric + quanity to determine size of hole. nba.m$var2 = as.numeric(nba.m$variable) + 15  # Labels and breaks need to be added with scale_y_discrete. y_labels = levels(nba.m$variable) y_breaks = seq_along(y_labels) + 15  p2 = ggplot(nba.m, aes(x=Name, y=var2, fill=value)) +      geom_tile(colour="white") +      scale_fill_gradient(low = "white", high = "steelblue") +      ylim(c(0, max(nba.m$var2) + 0.5)) +      scale_y_discrete(breaks=y_breaks, labels=y_labels) +      coord_polar(theta="x") +      theme(panel.background=element_blank(),            axis.title=element_blank(),            panel.grid=element_blank(),            axis.text.x=element_blank(),            axis.ticks=element_blank(),            axis.text.y=element_text(size=5))   ggsave(filename="plot_2.png", plot=p2, height=7, width=7) 

Answer 2

Addressing @FedericoGiorgi's comment, not the original question. Thanks @bdemarest your solution is incredibly useful!

Hack together a data frame to display labels, arrange them nicely:

nba.labs <- subset(nba.m, variable==levels(nba.m$variable)[nlevels(nba.m$variable)]) nba.labs <- nba.labs[order(nba.labs$Name),] nba.labs$ang <- seq(from=(360/nrow(nba.labs))/1.5, to=(1.5*(360/nrow(nba.labs)))-360, length.out=nrow(nba.labs))+80 nba.labs$hjust <- 0 nba.labs$hjust[which(nba.labs$ang < -90)] <- 1 nba.labs$ang[which(nba.labs$ang < -90)] <- (180+nba.labs$ang)[which(nba.labs$ang < -90)] 

Add a geom_text for labels:

p2 = ggplot(nba.m, aes(x=Name, y=var2, fill=value)) +      geom_tile(colour="white") +      geom_text(data=nba.labs, aes(x=Name, y=var2+1.5,         label=Name, angle=ang, hjust=hjust), size=3) +      scale_fill_gradient(low = "white", high = "steelblue") +      ylim(c(0, max(nba.m$var2) + 1.5)) +      scale_y_discrete(breaks=y_breaks, labels=y_labels) +      coord_polar(theta="x") +      theme(panel.background=element_blank(),            axis.title=element_blank(),            panel.grid=element_blank(),            axis.text.x=element_blank(),            axis.ticks=element_blank(),            axis.text.y=element_text(size=5)) print(p2)