Error Message - geom_path: Each group consists of only one observation. Do you need to adjust the group aesthetic?

[annier]

Hello! I am a very new R user and am trying to create a facet-wrapped line graph with each group highlighted in its own little graph, so I can avoid a spaghetti line graph. (Like the graph at the bottom of this page: The Spaghetti plot).

However, when I use my own data, I'm getting the error message: geom_path: Each group consists of only one observation. Do you need to adjust
the group aesthetic?
-- I'm not sure what this means - If I don't facet wrap, I can pull one group out of the spaghetti and highlight it without a problem.

I'm pasting in my code here. Any thoughts are very welcome! I'm totally stuck!

tmp %>%
  ggplot( aes(x=Years, y=Amount)) +
  geom_line( data=tmp %>% dplyr::select(-Good), aes(group=Good2), color="grey", size=0.5, alpha=0.5) +
  geom_line( aes(color=Good), color="#69b3a2", size=1.2 )+
  scale_color_viridis(discrete = TRUE) +
  theme_ipsum() +
  theme(
    legend.position="none",
    plot.title = element_text(size=14),
    panel.grid = element_blank()
  ) +
  ggtitle("English Exports to Africa, 1699-1800") +
  facet_wrap(~Good)
#> Error in tmp %>% ggplot(aes(x = Years, y = Amount)): could not find function "%>%"

[technocrat]

See the FAQ: How to do a minimal reproducible example reprex for beginners. This is missing data to work with. It's harder to attract answers if the problem has to be reverse engineered.