Julia DataFrames,在特定索引处插入新行 [英] Julia DataFrames, Insert new row at specific index
问题描述
是否可以在特定索引处向现有数据框添加一行?
Is there a way to add a row to an existing dataframe at a specific index?
例如您有一个包含3行1列的数据框
E.g. you have a dataframe with 3 rows and 1 columns
df = DataFrame(x = [2,3,4])
X
2
3
4
任何执行以下操作的方法:
any way to do the following:
insert!(df, 1, [1])
为了获得
X
1
2
3
4
我知道我可能可以合并两个数据帧df = [df1; df2],但我希望每当要插入一行时都避免对大型DF进行垃圾处理.
I know that i could probably concat two dataframes df = [df1; df2] but i was hoping to avoid garbaging a large DF whenever i want to insert a row.
推荐答案
我想您想就地进行.然后,您可以像这样使用insert!
函数:
I guess you want to do it in place. Then you can use insert!
function like this:
julia> df = DataFrame(x = [1,2,3], y = ["a", "b", "c"])
3×2 DataFrames.DataFrame
│ Row │ x │ y │
├─────┼───┼───┤
│ 1 │ 1 │ a │
│ 2 │ 2 │ b │
│ 3 │ 3 │ c │
julia> foreach((v,n) -> insert!(df[n], 2, v), [4, "d"], names(df))
julia> df
4×2 DataFrames.DataFrame
│ Row │ x │ y │
├─────┼───┼───┤
│ 1 │ 1 │ a │
│ 2 │ 4 │ d │
│ 3 │ 2 │ b │
│ 4 │ 3 │ c │
当然,您必须确保添加的集合中的列数正确.
Of course you have to make sure that you have the right number of columns in the added collection.
如果您接受使用DataFrame
的未导出内部结构,则可以做得更简单:
If you accept using unexported internal structure of a DataFrame
you can do it even simpler:
julia> df = DataFrame(x = [1,2,3], y = ["a", "b", "c"])
3×2 DataFrames.DataFrame
│ Row │ x │ y │
├─────┼───┼───┤
│ 1 │ 1 │ a │
│ 2 │ 2 │ b │
│ 3 │ 3 │ c │
julia> insert!.(df.columns, 2, [4, "d"])
2-element Array{Array{T,1} where T,1}:
[1, 4, 2, 3]
String["a", "d", "b", "c"]
julia> df
4×2 DataFrames.DataFrame
│ Row │ x │ y │
├─────┼───┼───┤
│ 1 │ 1 │ a │
│ 2 │ 4 │ d │
│ 3 │ 2 │ b │
│ 4 │ 3 │ c │
更新
因为Julia 1.0 df.columns
无法正常工作.而是写:
Since Julia 1.0 df.columns
does not work. Instead write:
insert!.(eachcol(df, false), 2, [4, "d"])
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