Colour related aesthetics: colour, fill and alpha

Description

This page demonstrates the usage of a sub-group of aesthetics; colour, fill and alpha.

Examples

# Bar chart example c <- ggplot(mtcars, aes(factor(cyl))) # Default plotting c + geom_bar()

# To change the interior colouring use fill aesthetic c + geom_bar(fill = "red")

# Compare with the colour aesthetic which changes just the bar outline c + geom_bar(colour = "red")

# Combining both, you can see the changes more clearly c + geom_bar(fill = "white", colour = "red")

# The aesthetic fill also takes different colouring scales # setting fill equal to a factor variable uses a discrete colour scale k <- ggplot(mtcars, aes(factor(cyl), fill = factor(vs))) k + geom_bar()

# Fill aesthetic can also be used with a continuous variable m <- ggplot(faithfuld, aes(waiting, eruptions)) m + geom_raster()

m + geom_raster(aes(fill = density))

# Some geoms don't use both aesthetics (i.e. geom_point or geom_line) b <- ggplot(economics, aes(x = date, y = unemploy)) b + geom_line()

b + geom_line(colour = "green")

b + geom_point()

b + geom_point(colour = "red")

# For large datasets with overplotting the alpha # aesthetic will make the points more transparent df <- data.frame(x = rnorm(5000), y = rnorm(5000)) h <- ggplot(df, aes(x,y)) h + geom_point()

h + geom_point(alpha = 0.5)

h + geom_point(alpha = 1/10)

# Alpha can also be used to add shading j <- b + geom_line() j

yrng <- range(economics$unemploy) j <- j + geom_rect(aes(NULL, NULL, xmin = start, xmax = end, fill = party), ymin = yrng[1], ymax = yrng[2], data = presidential) j

j + scale_fill_manual(values = alpha(c("blue", "red"), .3))