如何检查列是否有有效值？

Question

我需要从现有列派生一列后，检查是否有有效的条目没有。 INPUT

ID 
    2 

    4 
    6 


    34 

输出

ID ID_ENTRY 
2 PRESENT 
    NOT PRESENT 
4 PRESENT 
6 PRESENT 
    NOT PRESENT 
    NOT PRESENT 
34 PRESENT 

Answer 1

这里的一个基础R选项是使用ifelse：

df$ID_ENTRY <- ifelse(ID != "", "PRESENT", "NOT PRESENT") 

如果你能有空字符串，null或NA遗漏值那么我们可以使用：

df$ID_ENTRY <- ifelse(ID != "" & !is.na(ID) & !is.null(ID), 
         "PRESENT", "NOT PRESENT") 

Answer 2

通常，这可以用is.na解决：

dat[,"ID_ENTRY"] <- ifelse(is.na(dat[,"ID"]), "NOT PRESENT", "PRESENT") 

但是，有时有必要检查所讨论的列的类型和在这种情况下使用不同的方法。举例来说，如果它character列，该方法是

dat[, "ID_ENTRY"] <- ifelse(dat[,"ID"]=="", "NOT PRESENT", "PRESENT") 

Answer 3

使用可以使用sapply。

vec1 <- c("a", "b", "c", "") 
vec2 <- sapply(vec1, function(x){ifelse(x == "", "NOT PRESENT", "PRESENT")}) 
vec2 
## "PRESENT"  "PRESENT"  "PRESENT" "NOT PRESENT" 

Answer 4

假设ID是factor

ss <- data.frame(ID = c(2,' ',4,6,' ',' ',34)) 

> ss$ID_ENTRY <- lapply(ss$ID,function(x){ifelse(is.na(as.numeric(as.character(x))),'NOTPRESENT','PRESENT')}) 
> ss 
    ID ID_ENTRY 
1 2 PRESENT 
2 NOTPRESENT 
3 4 PRESENT 
4 6 PRESENT 
5 NOTPRESENT 
6 NOTPRESENT 
7 34 PRESENT 
>