Any way to extend the line in the legend?

Question

Let us say I have the following graph plotted using ggplot:

Is there anyway to extend how much line length is displayed in the legend? Sometimes, it just gets impossible to identify which line correspond to which line in the graph using the legend.

Answer 1

here is an option legend.key.width:

# sample data frame
df <- data.frame(x = c(rnorm(100, -3), rnorm(100), rnorm(100, 3)), 
                 g = gl(3, 100))
df <- ddply(df, .(g), summarize, x = x, y = ecdf(x)(x))

ggplot(df, aes(x, y, colour = g, linetype = g)) + 
    geom_line() + 
    theme(legend.key.width = unit(10, "line"))