根据多种条件过滤组内的行 [英] Filter rows within groups based on multiple conditions

问题描述

我有一个数据集，我想在其中过滤不同组中的行.

I have a data set where I would like to filter rows within different groups.

给出此数据框:

group = as.factor(c(1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3))   
fruit = as.factor(c("apples", "apples", "apples", "oranges", 
                    "oranges", "apples", "oranges",
                    "bananas", "bananas", "oranges", "bananas")) 
hit = c(1, 0, 1, 1, 
        0, 1, 1,
        1, 0, 0, 1)

dt = data.frame(group, fruit, hit) 
dt
   group   fruit hit
      1  apples   1
      1  apples   0
      1  apples   1
      1 oranges   1
      2 oranges   0
      2  apples   1
      2 oranges   1
      3 bananas   1
      3 bananas   0
      3 oranges   0
      3 bananas   1

我想使用组中第一次出现的fruit来过滤组.但是还有另一个条件，我只想保留hit等于1的那排水果.

I would like to use the first occurrence of fruit within a group to filter the groups. But there is another condition, I would only like keep the rows of that fruit where the hit is equal to 1.

因此，对于group 1，apples是第一次出现，并且具有两次正面命中率，因此我想保留这两行.

So, for group 1, apples is the first occurrence, and it has two times a positive hit, thus I I would like to keep those two rows.

结果如下:

  group   fruit hit
     1  apples   1
     1  apples   1
     2 oranges   1
     3 bananas   1
     3 bananas   1

我知道您可以使用dplyr进行过滤，但是我不确定是否可以实现.

I know you can filter with dplyr but I am not sure I can achieve this.

推荐答案

我们可以使用dplyr.按分组"分组后，filter具有"hit"不等于0的行和(&)作为"fruit"的first元素的

We can use dplyr. After grouping by 'group', filter the rows that have 'hit' not equal to 0 and (&) the 'fruit' as the first element of 'fruit'

library(dplyr)
dt %>%
   group_by(group) %>%
   filter(hit!=0 & fruit == first(fruit))
#   group   fruit   hit
#  <fctr>  <fctr> <dbl>
#1      1  apples     1
#2      1  apples     1
#3      2 oranges     1
#4      3 bananas     1
#5      3 bananas     1

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