How to add custom series labels to a legend in R's ggplot?

Question

I have a plot (sample code pasted below) that I am trying to add by own labels for the series information. Instead of plotting "p1s1" "p1s2" "p3s4", I would like "treatment 1" "treatment 2" "treatment 3". I have used levels(series_id) to get the unique series names and used a lookup table to get the descriptions. (I think this gets them in the same order they are plotted?) and I have these descriptions in a vector called treatment_descriptions.

From the documentation I think that I should be using a scale here, but I can't figure out which one, or how to do it. Something like: scale_something(name="Treatment Descriptions", breaks=NULL, labels=treatment_descriptions, formatter=NULL) ? But where should this go?

library(ggplot2)

# Create a long data.frame to store data...
growth_series = data.frame ("read_day" = c(0, 3, 9, 0, 3, 9, 0, 2, 8), 
"series_id" = c("p1s1", "p1s1", "p1s1", "p1s2", "p1s2", "p1s2", "p3s4", "p3s4", "p3s4"),
"mean_od" = c(0.6, 0.9, 1.3, 0.3, 0.6, 1.0, 0.2, 0.5, 1.2),
"sd_od" = c(0.1, 0.2, 0.2, 0.1, 0.1, 0.3, 0.04, 0.1, 0.3),
"n_in_stat" = c(8, 8, 8, 8, 7, 5, 8, 7, 2)
)

> # Now gives us some example long form data...
> > growth_series 
>  read_day series_id mean_od sd_od        n_in_stat   
>   1       p1s1     0.6      0.10         8 2       
>   3       p1s1     0.9      0.20         8 3    
>   9       p1s1     1.3      0.20         8 4    
>   0       p1s2     0.3      0.10         8 5    
>   3       p1s2     0.6      0.10         7 6    
>   9       p1s2     1.0      0.30         5 7    
>   0       p3s4     0.2      0.04         8 8    
>   2       p3s4     0.5      0.10         7 9    
>   8       p3s4     1.2      0.30         2 2

# Plot using ggplot...
ggplot(data = growth_series, aes(x = read_day, y = mean_od, group = series_id, color = series_id)) +
geom_line(size = 1.5) +
geom_point(aes(size = n_in_stat)) +
geom_errorbar(aes(ymin = mean_od - sd_od, ymax = mean_od + sd_od), size = 1, width = 0.3) +
xlab("Days") + ylab("Log (O.D. 730 nm)") +
scale_y_log2() +
scale_colour_hue('my legend', breaks = levels(growth_series$series_id), labels=c('t1', 't2', 't3'))

Answer 1

maybe you can relabel your factor?

growth_series$series_id <- factor(
     growth_series$series_id, 
     labels=c('treatment 1', 't2', 't3'))

Or if you are still looking for scale_something, it should be scale_colour_hue()

... + scale_colour_hue('my legend', 
   breaks = levels(growth_series$series_id), 
   labels=c('t1', 't2', 't3'))