aes_colour_fill_alpha {ggplot2} | R Documentation

## 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))

[Package ggplot2 version 2.1.0 Index]