如何合并 R 中的两列？

Question

我的数据框有 2 列，看起来与此类似：

a    b

NA   NA
yes  NA
no   NA
yes  NA
NA   yes
NA   no 
NA   NA
Na   yes

我想要的输出是：

ab

NA
yes
no
yes
yes
no
NA
yes

注意：

在原来的列中，任何给定行中总会有一个 NA。
对于某些行，两列都将为 NA

知道如何获得所需的输出吗？

Answer 1

使用dplyr你可以把它包裹得非常整齐:

library(dplyr)

df %>% rowwise() %>% summarize(ab = max(a,b, na.rm = T))

Answer 2

dat <- data.frame(a = c(NA, "yes", "no", "yes", NA, NA, NA, NA),
                  b = c(NA, NA, NA, NA, "yes", "no", NA, "yes"))

require(tidyverse)

dat %>% 
  rowwise() %>% 
  mutate(ab = max(a,b, na.rm = TRUE))

Answer 3

使用apply:

> apply(df, 1, max, na.rm=TRUE)
[1] NA    "yes" "no"  "yes" "yes" "no"  NA    "yes"

作业：

df$ab <- apply(df, 1, max, na.rm=TRUE)

Answer 4

dplyr::coalesce

> with(dat, dplyr::coalesce(a, b))
[1] NA    "yes" "no"  "yes" "yes" "no"  NA    "yes"

ifelse 用于基数 R

> with(dat, ifelse(!is.na(a), a, ifelse(!is.na(b), b, NA)))
[1] NA    "yes" "no"  "yes" "yes" "no"  NA    "yes"

max.col 基数 R

> dat[cbind(1:nrow(dat), max.col(!is.na(dat)))]
[1] NA    "yes" "no"  "yes" "yes" "no"  NA    "yes"

Answer 5

# Import data: df => data.frame 
df <- structure(list(a = c(NA, "yes", "no", "yes", NA, NA, NA, NA), 
b = c(NA, NA, NA, NA, "yes", "no", NA, "yes")), class = "data.frame", row.names = c(NA, 
-8L))

# Function to coalesce vectors: br_coalesce => function
br_coalesce <- function(...){
   # Coalesce vectors or data.frames: res => vector
   res <- Reduce(function(x, y) {
         x <- replace(x, is.na(x), y[is.na(x)])
      },
      list(...)
   )
   # Explicitly define returned vectors: character vector => env
   return(res)
}

# Apply function: character vector / data.frame => stdout(console)
br_coalesce(df$a, df$b)

Tidyverse 解决方案：

library(tidyverse)
df %>% 
   transmute(res = coalesce(a, b))

data.table 解决方案：

library(data.table)
fcoalesce(df$a, df$b)

如何合并 R 中的两列？

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