Question

我有一个包含许多国家/地区的数据框，它们的总病例数和不同日期的新病例数。它看起来如下：

  iso_code continent     location date       total_cases new_cases stringency_index population
  <chr>    <chr>         <chr>    <chr>            <dbl>     <dbl>            <dbl>      <dbl>
1 ABW      North America Aruba    2020-03-13           2         2              0       106766
2 ABW      North America Aruba    2020-03-19          NA        NA             33.3     106766
3 ABW      North America Aruba    2020-03-20           4         2             33.3     106766
4 ABW      North America Aruba    2020-03-21          NA        NA             44.4     106766
5 ABW      North America Aruba    2020-03-22          NA        NA             44.4     106766
6 ABW      North America Aruba    2020-03-23          NA        NA             44.4     106766

我能够过滤数据框以获取new_cases> = 5的所有行：

df_filtered <- df %>% filter(new_cases >= 5)

但是，这为我提供了new_cases等于或大于5的所有行：

  iso_code continent     location date       total_cases new_cases stringency_index population
  <chr>    <chr>         <chr>    <chr>            <dbl>     <dbl>            <dbl>      <dbl>
1 ABW      North America Aruba    2020-03-24          12         8             44.4     106766
2 ABW      North America Aruba    2020-03-25          17         5             44.4     106766
3 ABW      North America Aruba    2020-03-27          28         9             44.4     106766
4 ABW      North America Aruba    2020-03-30          50        22             85.2     106766
5 ABW      North America Aruba    2020-04-01          55         5             85.2     106766
6 ABW      North America Aruba    2020-04-03          60         5             85.2     106766

我怎么只能获得具有该条件的最早/第一日期的行？

这是我的输出理想的样子：

  iso_code continent     location           date       total_cases new_cases stringency_index population
  <chr>    <chr>         <chr>              <chr>            <dbl>     <dbl>            <dbl>      <dbl>
1 ABW      North America Aruba              2020-03-24          12         8             44.4     106766
2 AFG      Asia          Afghanistan        2020-03-16          16         6             38.9     38928341
3 AGO      Africa        Angola             2020-04-19          24         5             90.7     32866268
4 ALB      Europe        Albania            2020-03-13          23        12             78.7     2877800
5 AND      Europe        Andorra            2020-03-17          14         9             31.4     77265
6 ARE      Asia          Utd. Arab Emirates 2020-02-28          19         6              8.3     9890400

Answer 1

尝试一下：

df %>% 
  group_by(iso_code) %>%  ## within each country (group)
  filter(new_cases >= 5) %>%  ## keep rows where there are at least 5 cases
  slice_min(date, n = 1, with_ties = FALSE)  ## then keep the row with the smallest date

Answer 2

我可以将其与以下代码一起使用：

df_filtered <- df %>% filter(new_cases >= 5) #filter all new_cases with at least 5

df_sorted <- df_filtered %>%                 #group by country and arrange by date,
  group_by(iso_code) %>%                     #then get the first row of every 
  arrange(date) %>%                          #group 
  slice(1L)

受此问题Earliest Date for each id in R的答案的启发

如何根据日期和值从数据框中选择行？

2 个答案: