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!