Xtykutl

I have a data frame like these:

  NUM_TURNO CODIGO_MUNICIPIO SIGLA_PARTIDO     SHARE

1         1            81825           PPB 38.713318

2         1            81825          PMDB 61.286682

3         1            09717          PMDB 48.025900

4         1            09717            PL  1.279217

5         1            09717           PFL 50.694883

6         1            61921          PMDB 51.793868

This is a data.frame of elections in Brazil. Grouping by NUM_TURNO and CODGIDO_MUNICIPIO I want to compare the SHARE of the FIRST and SECOND most votted politics in each city and round (1 or 2) and create a new column.

What am I having problem to do? I don't know how to calculate the difference only for the two biggest SHARES of votes.

For the first case, for example, I want to create something that gives me the difference between 61.286682 and 38.713318 = 22.573364 and so on.

Something like this:

df %>%

    group_by(NUM_TURNO, CODIGO_MUNICIPIO) %>%

    mutate(Diff = HIGHER SHARE - 2º HIGHER SHARE))

You could arrange your dataframe by Share and then slice the first two values. Then you could use summarise to get the diff between the values for every group:

library(dplyr)

df %>%

    group_by(NUM_TURNO, CODIGO_MUNICIPIO) %>%

    arrange(desc(Share)) %>%

    slice(1:2) %>%

    summarise(Diff = -diff(Share))

You can also use top_n from dplyr with grouping and summarizing. Keep in mind that in the data you provided, you will get an error in summarize if you use diff with a single value, hence the use of ifelse.

df %>%

  group_by(NUM_TURNO, CODIGO_MUNICIPIO) %>%

  top_n(2, SHARE) %>% 

  summarize(Diff = ifelse(n() == 1, NA, diff(SHARE)))



# A tibble: 3 x 3

# Groups:   NUM_TURNO [?]

  NUM_TURNO CODIGO_MUNICIPIO  Diff

      <dbl>            <dbl> <dbl>

1         1             9717  2.67

2         1            61921 NA   

3         1            81825 22.6