r - ans[npos] <- rep(no, length.out = len)[npos] 错误 : replacement has length zero

Question

您好，我目前是一年级学生，仍在学习 R 在线类(class)，我收到一条错误消息:“ans[npos] <- rep(no, length.out = len)[npos] 中的错误:替换的长度为零另外: 警告信息:在 rep(no, length.out = len) : 'x' is NULL so the result will be NULL"in R studio 我不知道为什么这样做，我使用 read.csv 获取数据并获取第二个列，然后取第二列的前两项，然后将第一项与第二列的第三项进行比较，这是我的代码:

dataGrade <- read.csv(file.choose(), fileEncoding = "UTF-8-BOM")

gradeColumn2 <- dataGrade[, 2]
twoGrades <- gradeColumn2[1:2]

ifelse(twoGrades[1] == gradeColumn2[3],
       cat("Grade", twoGrades[1],"is equal to Grade",gradeColumn2[3]),
       cat("Grade", twoGrades[1],"is not equal to Grade",gradeColumn2[3]))

csv文件中的数据为

Answer 1

因为您正在检查长度为 1 的条件，所以使用 if/else 而不是 ifelse。

dataGrade <- data.frame(GRADE.A = c(79, 89, 93),
                        GRADE.B = c(90, 92, 91))

gradeColumn2 <- dataGrade[, 2]
twoGrades <- gradeColumn2[1:2]

if(twoGrades[1] == gradeColumn2[3]) {
  cat("Grade", twoGrades[1],"is equal to Grade",gradeColumn2[3])
} else{
    cat("Grade", twoGrades[1],"is not equal to Grade",gradeColumn2[3])
}

#Grade 90 is not equal to Grade 91