一次检查多个数据框列（灵活方式）

Question

寻找更好的方法：如何使 R 按元素检查多列的灵活子集的值（假设此处为 Var2 和 Var3）并写入结果检查新的逻辑列？

这里有比按行 apply() 更短、更优雅的方法吗？

df <- read.csv(
  text = '"Var1","Var2","Var3"
  "","",""
  "","","a"
  "","a",""
  "a","a","a"
  "a","","a"
  "","a",""
  "","",""
  "","","a"
  "","a",""
  "","","a"'
)

criticalColumns <- c("Var2", "Var3")

df$criticalColumnsAreEmpty <-
  apply(df[, criticalColumns], 1, function(curRow) {
    return(all(curRow == ""))
  })

我也可以明确地做到这一点，但这并不灵活：

df$criticalColumnsAreEmpty <- df$Var2 == "" & df$Var3 == ""

期望的输出：

 Var1 Var2 Var3 criticalColumnsAreEmpty
                                   TRUE
              a                   FALSE
         a                        FALSE
    a    a    a                   FALSE
    a         a                   FALSE
         a                        FALSE
                                   TRUE
              a                   FALSE
         a                        FALSE
              a                   FALSE

Answer 1

我们可以在逻辑矩阵

上使用rowSums

df$criticalColumnsAreEmpty <- !rowSums(df[criticalColumns]!="")
df$criticalColumnsAreEmpty
#[1]  TRUE FALSE FALSE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE

或另一种选择（对于大数据集，以避免因内存原因转换为矩阵）在列上循环，检查元素是否为空白并使用 Reduce 和 &

Reduce(`&`, lapply(df[criticalColumns], function(x) !nzchar(as.character(x))))

一次检查多个数据框列（灵活方式）

Checking multiple data frame columns at once (flexible manner)

r

vectorization

apply

dataframe