Question

我试图实例化一个数据框，然后在其中插入行。其中一列将包含字符串。我将字符串视为因素存在问题，然后当出现新字符串时，R会插入NA。所以我不得不使用以下解决方法：

df = data.frame(x = character(3), stringsAsFactors = F)
df = rbind(df, c('foo'))
df = rbind(df, c('bar'))
df
#    x
#1    
#2    
#3    
#4 foo
#5 bar

然而，它并不好，因为我不想要空行。但是以下方法不起作用：

df = data.frame(x = character(0), stringsAsFactors = F)
df = rbind(df, c('foo'))
df = rbind(df, c('bar'))
#Warning message:
#In `[<-.factor`(`*tmp*`, ri, value = "bar") :
#  invalid factor level, NA generated

我知道我可以使用df[i, ] = c(...)，但我不想跟踪索引。

Answer 1

使用list：

rbind(df, list(x=c("foo","bar")))
#    x
#1 foo
#2 bar

Answer 2

默认情况下，

rbind为stringsAsFactors=TRUE。因此，请使用stringsAsFactors=FALSE以避免转换为factor类

根据?rbind

rbind（...，deparse.level = 1，make.row.names = TRUE， stringsAsFactors = default.stringsAsFactors（））

df <- rbind(df, list(x='foo'), stringsAsFactors= FALSE)
df <- rbind(df, list(x = 'bar'), stringsAsFactors = FALSE)
df
#   x
#1 foo
#2 bar

str(df)
#'data.frame':   2 obs. of  1 variable:
# $ x: chr  "foo" "bar"

我们也可以在stringsAsFactors中更改options，而不是重复使用data.frame。

这里我们假设OP想要按顺序添加行，并根据OP character（'df'）的初始化，列类将是def reconstruct_path(came_from, start, goal): current = goal path = [current] while current != start: current = came_from[current] path.append(current) path.reverse() # optional return path class

Answer 3

确保使用rbind加入具有相同列名的data.frames

df = data.frame(x = character(0), stringsAsFactors = FALSE)
df = rbind(df, data.frame(x = c('foo')))
df = rbind(df, data.frame(x = c('bar')))
df
#    x
#1 foo
#2 bar

Answer 4

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tidy

列字符类型的数据框不适用于rbind

4 个答案: