geom_tile

geom_tile(mapping=NULL, data=NULL, stat="identity", position="identity", ...)

What do you think of the documentation? Please let me know by filling out this short online survey.

Aesthetics

The following aesthetics can be used with geom_tile. Aesthetics are mapped to variables in the data with the aes function: geom_tile(aes(x = var)). Note that you do not need quotes around the variable name.

Scales control how the variable is mapped to the aesthetic and are listed after each aesthetic.

Aesthetic	Default	Related scales
x	required	continuous, date, datetime, discrete
y	required	continuous, date, datetime, discrete
fill	grey20	brewer, gradient, gradient2, gradientn, grey, hue, identity, manual
colour	NA	brewer, gradient, gradient2, gradientn, grey, hue, identity, manual
size	0.1	identity, manual, size
linetype	1	identity, linetype, manual
alpha	1

Layers are divided into groups by the group aesthetic. By default this is set to the interaction of all categorical variables present in the plot.

Parameters

Parameters control the appearance of the geom. In addition to the parameters listed below (if any), any aesthetic can be used as a parameter, in which case it will override any aesthetic mapping.

Returns

This function returns a layer object.

Examples

> # Generate data 
> pp <- function (n,r=4) { 
+  x <- seq(-r*pi, r*pi, len=n) 
+  df <- expand.grid(x=x, y=x) 
+  df$r <- sqrt(df$x^2 + df$y^2) 
+  df$z <- cos(df$r^2)*exp(-df$r/6) 
+  df 
+ } 
> p <- ggplot(pp(20), aes(x=x,y=y)) 
>  
> p + geom_tile() #pretty useless! 
  
>  
> # Add aesthetic mappings 
> p + geom_tile(aes(fill=z)) 
  
>  
> # Change scale 
> p + geom_tile(aes(fill=z)) + scale_fill_gradient(low="green", high="red") 
  
>  
> # Use qplot instead 
> qplot(x, y, data=pp(20), geom="tile", fill=z) 
  
> qplot(x, y, data=pp(100), geom="tile", fill=z) 
  
>  
> # Missing values 
> p <- ggplot(pp(20)[sample(20*20, size=200),], aes(x=x,y=y,fill=z)) 
> p + geom_tile() 
  
>  
> # Input that works with image 
> image(t(volcano)[ncol(volcano):1,]) 
> ggplot(melt(volcano), aes(x=X1, y=X2, fill=value)) + geom_tile() 
  
>  
> # inspired by the image-density plots of Ken Knoblauch 
> cars <- ggplot(mtcars, aes(y=factor(cyl), x=mpg)) 
> cars + geom_point() 
  
> cars + stat_bin(aes(fill=..count..), geom="tile", binwidth=3, 
+ position="identity") 
  
> cars + stat_bin(aes(fill=..density..), geom="tile", binwidth=3, 
+ position="identity") 
  
>  
> cars + stat_density(aes(fill=..density..), geom="tile", position="identity") 
  
> cars + stat_density(aes(fill=..count..), geom="tile", position="identity") 
  
>  
> # Another example with with unequal tile sizes 
> x.cell.boundary <- c(0, 4, 6, 8, 10, 14) 
> example <- data.frame( 
+   x = rep(c(2, 5, 7, 9, 12), 2), 
+   y = factor(rep(c(1,2), each=5)), 
+   z = rep(1:5, each=2), 
+   w = rep(diff(x.cell.boundary), 2) 
+ ) 
>  
> qplot(x, y, fill=z, data=example, geom="tile") 
  
> qplot(x, y, fill=z, data=example, geom="tile", width=w) 
  
> qplot(x, y, fill=factor(z), data=example, geom="tile", width=w) 
  
>  
> # You can manually set the colour of the tiles using 
> # scale_manual 
> col <- c("darkblue", "blue", "green", "orange", "red") 
> qplot(x, y, fill=col[z], data=example, geom="tile", width=w, group=1) + 
+ scale_fill_identity(labels=letters[1:5], breaks=col) 
  

What do you think of the documentation? Please let me know by filling out this short online survey.

© Hadley Wickham 2010