Group data and plot multiple lines

Question

I\'d like to plot multiple lines in R for this dataset: (x = Year, y = Value)

School_ID   Year    Value
A           1998    5
B           1998    10
C                


        

Answer 1

The plot function in base R does not support grouping so you need to display your groups one by one. GGPLOT handles grouping well. I also suggest looking at Trellis XYPLOT which allows you to plot separate groups.

This is how you can create a basic grouped line plot using Trellis:

library(lattice)
rm(list = ls())     # clear objects  
graphics.off()      # close graphics windows   

test = data.frame(x =  rep(1:3, each = 2),
                  group =  rep(c("Group 1","Group 2"),3),
                  y=   c(22,8,11,4,7,5)
                 )
xyplot(y~x,
       type="b",
       group=group,
       data=test,
       auto.key =list(
         points = FALSE, 
         columns=2,
         lines = TRUE)
)