Remove grey fill for out of bounds values when using limits in scale_

Question

I am using R (3.0.1) and ggplot2 (ggplot2_0.9.3.1) with geom_tile and scale_fill_gradient. I am using the \'limits\' opti

Answer 1

Add the argument na.value="transparent" to scale_fill_gradient:

p + theme_bw() + geom_tile(aes(fill=z)) +
     scale_fill_gradient(low="green", high="red",
                         limits=c(-0.1, 0.1), na.value="transparent")