R中的if语句：尽管存在值，但仍存在”缺少值”错误

if-statement in R: “missing value” error despite existing value

如果存在完美的健康值，则if语句返回"缺少值"错误。

我想编写一个简单的脚本来删除数据集中的行(如果其中一个条目包含某个标记)。我在新列(containsMR)中分配了一个指标变量，然后使用for循环遍历各行。如果指示符为TRUE，则应删除该行。

到目前为止，指示器已正确分配，效果很好。有趣的部分：在循环的if语句中似乎无法读取值，因为它返回" if(data(containsMR [i]){
缺少需要TRUE / FALSE的值"。

给出正确(且完整)的指标变量分配，这让我感到惊讶。更奇怪的是：删除了一些但不是全部带有正指示符的行(使用打印输出和table(data $ containsMR)进行了检查)。

现在真的很奇怪：如果我再运行一次相同的循环，它将删除其余的列(应有的话)，但是返回相同的错误。因此，从理论上讲，我可以运行两次循环，忽略错误并获得想要的结果。那真的不是我在做什么的重点。

修正的修正：
-从for改为while循环
-将指标(和if语句)更改为整数(0,1)
-在RStudio和R控制台中运行脚本
-更改了变量名称，包括了/排除了定义(例如，添加代理变量row_number而不是一行调用它。

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# Script to delete all rows containing"MR" in column"EXAM_CODE"

# import file
data <- read.csv("C:\\\\ScriptingTest\\\\ablations 0114.csv")

# add indicator column
for (i in 1:nrow(data)){
data$containsMR[i] <- ifelse(grepl("MR", toString(data$EXAM_CODE[i])), TRUE, FALSE)
}

# remove rows with positive indicator
row_number <- nrow(data)
for (i in 1:row_number){
if (data$containsMR[i]){
data <- data[-c(i),]
}
}

# export csv
write.csv(data,"C:\\\\ScriptingTest\\\\export.csv")

相关讨论

为说明该问题正在修改要循环的for循环中对象的大小，请参见以下示例：

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n <- nrow(mtcars)

for (i in 1:n){
cat("\
mtcars currently has",nrow(mtcars),"rows;","accessing row",i)
if (mtcars$cyl[i] == 4){
mtcars <- mtcars[-i,]
}
}

> mtcars currently has 32 rows; accessing row 1
mtcars currently has 32 rows; accessing row 2
mtcars currently has 32 rows; accessing row 3
mtcars currently has 31 rows; accessing row 4
mtcars currently has 31 rows; accessing row 5
mtcars currently has 31 rows; accessing row 6
mtcars currently has 31 rows; accessing row 7
mtcars currently has 30 rows; accessing row 8
mtcars currently has 30 rows; accessing row 9
mtcars currently has 30 rows; accessing row 10
mtcars currently has 30 rows; accessing row 11
mtcars currently has 30 rows; accessing row 12
mtcars currently has 30 rows; accessing row 13
mtcars currently has 30 rows; accessing row 14
mtcars currently has 30 rows; accessing row 15
mtcars currently has 30 rows; accessing row 16
mtcars currently has 29 rows; accessing row 17
mtcars currently has 28 rows; accessing row 18
mtcars currently has 28 rows; accessing row 19
mtcars currently has 28 rows; accessing row 20
mtcars currently has 28 rows; accessing row 21
mtcars currently has 28 rows; accessing row 22
mtcars currently has 27 rows; accessing row 23
mtcars currently has 26 rows; accessing row 24
mtcars currently has 26 rows; accessing row 25
mtcars currently has 26 rows; accessing row 26
mtcars currently has 25 rows; accessing row 27
Error in if (mtcars$cyl[i] == 4) { :
missing value where TRUE/FALSE needed