dplyr verbs: group

Once again we assume that you've got the dataframe set up appropriately.

library(tidyverse)

# This command makes sure that the chickweight dataframe is clean.
df <- ChickWeight %>% ungroup() %>% as.data.frame()

We see how we can combine verbs to query the data.

df %>%
  filter(Time <= 10) %>%
  group_by(Time, Diet) %>%
  summarise(mean_weight = mean(weight), var_weight = var(weight), n = n())

Note that the image used in this video can originally be found over at software carpentry. It's a pretty cool learning source if you haven't seen it yet!