ans[npos]中出错<；-rep（否，length.out=len）[npos]：替换的长度为零

您好，我目前是大一新生，仍在学习R在线课程，我收到一条错误消息：

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“ans[NPO]中的错误，因为您正在检查长度1的条件，请使用

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

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dataGrade虽然答案是正确的，但原因是ifelse（）是条件元素选择，因此它被设计为返回一个值。您需要结构if/else来执行操作。
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