Filter tibble in R if variable observation appears in all groups

Question

library(tidyverse)

dta <- tibble(
  date = c("2000-01-01", "2000-01-02", "2000-01-03", "2000-01-02","2000-01-03"),
  stock = c("A", "A", "A", "B", "B"),
  price = c("price_{A1}","price_{A2}","price_{A3}","price_{B1}","price_{B2}" )
)

The data is given in this tibble (code above):

# A tibble: 5 x 3
  date       stock price     
  <chr>      <chr> <chr>     
1 2000-01-01 A     price_{A1}
2 2000-01-02 A     price_{A2}
3 2000-01-03 A     price_{A3}
4 2000-01-02 B     price_{B1}
5 2000-01-03 B     price_{B2}

I want to exclude row 1, since date 2000-01-01 is not available for all stocks in the tibble.

Answer 1

One option could be:

library(dplyr)

dta %>%
  group_by(date) %>%
  filter(n_distinct(stock) != 1)

# A tibble: 4 x 3
# Groups:   date [2]
  date       stock price     
  <chr>      <chr> <chr>     
1 2000-01-02 A     price_{A2}
2 2000-01-03 A     price_{A3}
3 2000-01-02 B     price_{B1}
4 2000-01-03 B     price_{B2}

Answer 2

Or:

library(tidyverse)

dta <- tibble(
  date = c("2000-01-01", "2000-01-02", "2000-01-03", "2000-01-02","2000-01-03"),
  stock = c("A", "A", "A", "B", "B"),
  price = c("price_{A1}","price_{A2}","price_{A3}","price_{B1}","price_{B2}" )
)

dta %>%
  filter(date %in% reduce(split(.$date, .$stock), intersect))

# date       stock price     
 <chr>      <chr> <chr>     
# 1 2000-01-02 A     price_{A2}
# 2 2000-01-03 A     price_{A3}
# 3 2000-01-02 B     price_{B1}
# 4 2000-01-03 B     price_{B2}