Here's how I want it to look (made in Excel):
And here's the template code:
library(ggplot2)
data <- c(0.3,0.4,0.5,0.6,0.7,0.8)
qplot(x=1:6, y=data, geom="bar", stat="identity")
Edited after commenter suggested I need more words in my question:
My code above draws the x-axis at y=0 so that all the bars go up from the axis. I want the x-axis to be at y=0.5 and I want bars with values < 0.5 to go down, while bars with values > 0.5 to go up. Like in the Excel plot I have placed above.
Hopefully this makes sense.