Replacing ggplot2 legend key for geom_line with symbol

Question

I have a line plot of prices for three stocks, which I normalise by taking the percentage change from the beginning of the period I am looking at. This seems to work fine, b

Answer 1

You can define new geom like this:

GeomLine2 <- proto(GeomLine, {
    objname <- "line2"
    guide_geom <- function(.) "polygon"
    default_aes <- function(.) aes(colour = "black", size=0.5, linetype=1, alpha = 1, fill = "grey20")
     })
geom_line2 <- GeomLine2$build_accessor()

chart1 <- ggplot(data=changes,aes(x=Date, y=value, colour=variable, fill = variable))
chart1 <- chart1 + geom_line2(lwd=0.5) + ylab("Change in price (%)") + xlab("Date") +
  labs(colour="Company",  fill = "Company")
print(chart1)

Not sure but note that this will not work in the next version of ggplot2.