ggplot2: how to color a graph by multiple variables

Two options:

library(ggplot2)

df <- data.frame(date = c("2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC"),
                 temp = c(80.24018,  85.88911, 104.23125,  85.13571,  91.21129, 104.88333,  97.81116, 107.40484, 121.03958,  87.91830),
                 id = c("A","A","A","A","A","B","B","B","B","B"),
                 location = c("N","S","S","N","N","S","N","S","N","S"))

df$date <- as.Date(df$date)    # parse dates to get a nicer x-axis

Map id to color and location to linetype:

ggplot(df, aes(date, temp, color = id, linetype = location)) + geom_path()

...or plot all interactions as different colors:

ggplot(df, aes(date, temp, color = id:location)) + geom_path()

I want to provide another way of doing that. I don't know why but color=id:location doesn't work for me. I solved it by using tidyr::unite

This way I did it:

library(ggplot2)

df <- data.frame(date = c("2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC", "2016-05-01 UTC", "2016-06-01 UTC", "2016-04-01 UTC"),
                 temp = c(80.24018,  85.88911, 104.23125,  85.13571,  91.21129, 104.88333,  97.81116, 107.40484, 121.03958,  87.91830),
                 id = c("A","A","A","A","A","B","B","B","B","B"),
                 location = c("N","S","S","N","N","S","N","S","N","S"))

df$date <- as.Date(df$date) 

df <- tidyr::unite(df,"id_loc",id,location,remove = F)
ggplot(df,aes(date, temp, color = id_loc)) + geom_path()

plot generated