Question

我有一个有三列的df。每列都有一个字符或NA，每行只有一个字符。就像这个例子：

df <- data.frame(a=c("NA","NA","NA","NA","fruits","fruits","fruits","fruits","fruits","fruits"), 
                 b=c("NA","NA","veggies","veggies","NA","NA","NA","NA","NA","NA"),
                 c=c("nuts","nuts","NA","NA","NA","NA","NA","NA","NA","NA") )

我想要将所有三列合并，以获得此结果：

1     nuts
2     nuts
3  veggies
4  veggies
5   fruits
6   fruits
7   fruits
8   fruits
9   fruits
10  fruits

使用数值我会aggregate使用na.rm=TRUE。但是，我不知道如何用字符来做这件事。想法？谢谢

Answer 1

我们可以在将字符串“NA”转换为真实max.col后使用NA。我们使用max.col获取行/列索引，提取值，然后转换为data.frame。

is.na(df) <- df=='NA'
data.frame(var=df[cbind(1:nrow(df),max.col(!is.na(df)))])
#      var
#1     nuts
#2     nuts
#3  veggies
#4  veggies
#5   fruits
#6   fruits
#7   fruits
#8   fruits
#9   fruits
#10  fruits

或另一种选择是

data.frame(var= df[cbind(1:nrow(df),(+!is.na(df)) %*% seq_along(df))])

Answer 2

要完善评论中提供的想法，您可以这样做：

data.frame(var = apply(df, 1, function(x) paste(gsub("NA", "", x), collapse = "")) )

      var
1     nuts
2     nuts
3  veggies
4  veggies
5   fruits
6   fruits
7   fruits
8   fruits
9   fruits
10  fruits

Answer 3

实际数据情况可能决定是否比逐行方法更好或更差。这是获得打印输出的一种方式，如您指定的那样：

> as.matrix( df[df!="NA"] )

或者可能更好：

> cat( paste( "\n", df[ df!="NA" ] ) )

 fruits 
 fruits 
 fruits 
 fruits 
 fruits 
 fruits 
 veggies 
 veggies 
 nuts 
 nuts

R：如何“聚合”（或组合）字符列？

3 个答案: