Customize background color of ggtitle

Question

I want to be able to change the background of the ggtitle of my ggplot to forestgreen while keeping the text white. The color shouldn't apply to the whole of the graph but only the title. This is what I have so far:

p <- ggplot(...)
p <- p + ggtitle("Market Updates") + labs(x = "Date", y = "High")
p <- p + theme(plot.title = element.text(hjust = 0.5, size = 20, 
               color = "#FFFFFF"))

I would like to make it look like this:

Answer 1

Update from comments.

There are a couple of approaches to do this; using facet_, as Axeman suggests, to create a strip above the plot (it is easier to change the the format of the strip than the title strip) , or you can create a title strip manually and then glue it to the plot.

Example

library(ggplot2)
library(gridExtra)
library(grid)

# Create dummy variable to facet on: this name will appear in the strip
mtcars$tempvar <- "Market Updates"

# Basic plot
# Manually added legend to match your expected result
p <- ggplot(mtcars, aes(mpg, wt)) + 
        geom_line(aes(colour="Com")) +
        scale_colour_manual(name="", values=c(Com = "#228b22") ) +
        labs(x = "Date", y = "High")

Using facet_: this only adds the colour bar across the plot panel, although the title is centered.

p + facet_grid(. ~ tempvar) +
        theme(strip.background = element_rect(fill="#228b22"),
              strip.text = element_text(size=15, colour="white"))

Which produces

Using grid functions: this adds the colour bar across the plot panel, but the title is centered on the graphics window. (you could get a bit more control with positioning by adding it to the plot gtable)

my_g <- grobTree(rectGrob(gp=gpar(fill="#228b22")),
                 textGrob("Market Updates", x=0.5, hjust=0.5,
                                            gp=gpar(col="white", cex=1.5)))

grid.arrange(my_g, p, heights=c(1,9))

Which produces