ggplot: aes vs aes_string, or how to programmatically specify column names?

Question

Let\'s assume we have the following data frame

data <- data.frame(time=1:10, y1=runif(10), y2=runif(10), y3=runif(10))

and we want to create

Answer 1

You could melt (thanks for reminding me of this function, rawr) all of your data into a few columns. For example, it could look like this:

library(reshape2)    
data2 <- melt(data, id = "time")
head(data2)
#    time variable       value
# 1     1       y1 0.353088575
# 2     2       y1 0.621565368
# 3     3       y1 0.696031085
# 4     4       y1 0.507112969
# 5     5       y1 0.009560710
# 6     6       y1 0.158993988
ggplot(data2, aes(x = time, y = value, color = variable)) + geom_line()