Create graphs by group using ggplot in R

To achieve your desired result

1. Split your dataframe by group using e.g. split
2. Use lapply to loop over the list of splitted data frames to create your plots or if you want to add the group labels to the title you could loop over names(df_split).

Note: I converted the id variable to factor. Also, you have to map id on the group aesthetic to get lines per group. However, as your x variable is a numeric there is actually no need for the group aesthetic.

library(ggplot2)

df_split <- split(df, df$group)

lapply(df_split, function(df) {
  ggplot(df, aes(x = x, y = y, group = id, color = factor(id))) +
    geom_line()
})

lapply(names(df_split), function(i) {
  ggplot(df_split[[i]], aes(x = x, y = y, group = id, color = factor(id))) +
    geom_line() +
    labs(title = paste("group =", i))
})
#> [[1]]

#> 
#> [[2]]

And even I if would recommend to use lapply the same could be achieved using a for loop like so:

for (i in names(df_split)) {
  print(
    ggplot(df_split[[i]], aes(x = x, y = y, group = id, color = factor(id))) +
      geom_line() +
      labs(title = paste("group =", i))
  )
}