Elimination of observations that do not vary over the period with R (r-cran)

Question

Good evening!

I have a base with the following characteristic:

Year   source   destination   HS04   value
1989    ARG        BRA        0101     1
1989    ARG        BRA        0102     0
1989    ARG        BRA        0103     0
1989    ARG        BRA        0104     1
  .      .          .           .      .
  .      .          .           .      .
  .      .          .           .      .
2010    ARG        BRA        0101     1
2010    ARG        BRA        0102     1
2010    ARG        BRA        0103     1
2010    ARG        BRA        0104     1

I need to eliminate the HS04 observations that did not vary over the period. That is, HS04 0101 and HS04 0104 since both initial and final years had a value of 1.

The reference would be HS04, ie for a given pair of countries (eg ARG and BRA) HS04 varied between the initial period and the final period.

The sample period covers 1989-2010

Thanks in advance for your attention!

Answer 1

We can try

 data %>% group_by(HS04) %>% 
          mutate(flag = ifelse(min(value) & max(value)==1, 1, 0)) %>% 
          filter(flag==0) %>% ungroup()

Data

data <- read.table(text = "
               Year   source   destination   HS04   value
               1989    ARG        BRA        0101     1
               1989    ARG        BRA        0102     0
               1989    ARG        BRA        0103     0
               1989    ARG        BRA        0104     1
               2010    ARG        BRA        0101     1
               2010    ARG        BRA        0102     1
               2010    ARG        BRA        0103     1
               2010    ARG        BRA        0104     1
",header=T)

Answer 2

using @A. Suliman data, n_distinct() exactly fits your need:

data %>% group_by(HS04) %>% 
      filter(n_distinct(value) >1) %>% ungroup()