如何根据另一列中值的单一出现使一列中的所有值相同？

Posted 2023-01-23

因此，我有一个数据框，其中每个物种都具有从A-E得出的物种名称和等级，有时会出现相同物种的不同等级，但是我想要以下内容：如果一个物种甚至有一个X级出现，那么该物种的所有其他出现也必须是X级。这是我的数据框：

     species        |    grade      | 
-----------------------------------
Tilapia guineensis  | B |
Tilapia guineensis  | E |
Tilapia zillii      | A |
Fundulus rubrifrons | A |
Eutrigla gurnardus  | D |
Sprattus sprattus   | A |
Gadus morhua        | E |
Gadus morhua        | B |
Tilapia zillii      | C |
Gadus morhua        | B | 
Eutrigla gurnardus  | C |

到目前为止，我以E级为例进行了以下尝试：

 df<-df%>% left_join(df%>% 
                                   group_by(species) %>% 
                                   summarize(sum_e = sum(grade=='E')),by='species') %>%
    mutate(grade = ifelse(sum_e>0,"E",grade))

但是我得到了错误：

Error: `by` can't contain join column `species` which is missing from RHS

我想要的输出基本上是这个：

     species        |    grade      | 
-----------------------------------
Tilapia guineensis  | E |
Tilapia guineensis  | E |
Tilapia zillii      | C |
Fundulus rubrifrons | A |
Eutrigla gurnardus  | D |
Sprattus sprattus   | A |
Gadus morhua        | E |
Gadus morhua        | E |
Tilapia zillii      | C |
Gadus morhua        | B | 
Eutrigla gurnardus  | D |

答案

[这是我将使用data.table程序包解决的方法。我认为，如果更改为dplyr，则各阶段将相似，只是写法不同

# solution using data.table package
library(data.table)

# fake data, replace with yours
df <- data.frame(species=c("a", "a", "b", "b"),
                 grade=c("A", "E", "B", "C"))

# select your grade
dominant_grade <- "E"
# convert to data.table
dt <- as.data.table(df)
# search over species, add a column that checks if any of the grades is equal
# to the dominant one
dt[, contains_dominant := any(grade == dominant_grade), by=species]
# For cases where the dominant one is present, set all the grades to the dominant
# one
dt[contains_dominant == TRUE, grade := dominant_grade]

# convert back to data frame and trim for output
out <- setDF(dt[, .(species, grade)])
out