ggplot group by one categorical variable and color by a second one

Question

Basically I\'d like to create the first plot shown below in R using ggplot, but with both objects on the same graph (no facet wrapping).

Consider a minimal example

Answer 1

You could paste rep and variable a group:

ggplot(dat) + geom_line(aes(x, value, group = paste(variable, rep), color = variable), 
                    alpha = 0.3)