Count of Rows Grouped by Variable

Question

I'm trying to get a count of rows grouped by a certain variable using dplyr.

Example of the data below

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Get a count of eunits = 0 by state.

Code that does not work:

data  %>% select(state, eunit) %>% filter(eunit == 0) %>% summarise(nrow(.)) %>% group_by(state)

Error that comes up:

Error in grouped_df_impl(data, unname(vars), drop)

Answer 1

You need to reverse the order of group_by and summarise dplyr verbs. Also I'm not 100% sure that nrow(.) will work (it might, but I'm not in a placed to confirm). I typically use n() to count rows in a summarise verb.

data  %>% 
  select(state, eunit) %>% 
  filter(eunit == 0) %>% 
  group_by(state) %>%
  summarise(cnt = n()) 

Answer 2

You need to group by state first, then summarize and count:

data  %>% select(state, eunit) %>% filter(eunit == 0) %>% group_by(state) %>% summarise(n())