Question

Possible Duplicate:
Margin adjustments when using ggplot’s geom_tile()

How can I adjust the width between tick marks and the raster margin, as show in the image

Thanks.

Answer 1

You need to set expand=c(0, 0) in your axis scales.

You can read all about this in ?continuous_scale. Quoting:

expand
a numeric vector of length two, giving a multiplicative and
additive constant used to expand the range of the scales so that there
is a small gap between the data and the axes.

library(ggplot2)

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
}
ggplot(pp(20), aes(x=x,y=y)) + 
  geom_tile(aes(fill=z)) + 
  scale_fill_gradient(low="green", high="red") +
  scale_x_continuous(expand=c(0, 0)) + 
  scale_y_continuous(expand=c(0, 0))