Julia数据框列的总和，其中另一列的值在列表中。

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英文:

Sum of Julia Dataframe column where values of another column are in a list

问题

  1. 如何编写适用于Julia的一行代码，用于对“col1”中的值在“list”中的行的“col2”值求和？我对Julia还不太熟悉，尝试以下代码会出现错误“Exception has occurred: DimensionMismatch DimensionMismatch: arrays could not be broadcast to a common size; got a dimension with lengths 10 and 3” 
  1. total_sum = sum(df[ismember(df[:, :col1], list), :col2])
英文:

How do I make a line of code that works for Julia to sum the values of col2 where the values of col1 that are in list ? I'm pretty new to Julia and trying the following lines prints out the error Exception has occurred: DimensionMismatch
DimensionMismatch: arrays could not be broadcast to a common size; got a dimension with lengths 10 and 3

  1. total_sum = sum(df[ismember(df[:, :col1], list), :col2])

答案1

得分: 2

以下是已翻译的代码部分：

  1. julia> df = DataFrame(reshape(1:12,4,3),:auto)
  2. 4×3 DataFrame
  3.  Row │ x1     x2     x3    
  4.      │ Int64  Int64  Int64 
  5. ─────┼─────────────────────
  6.    1 │     1      5      9
  7.    2 │     2      6     10
  8.    3 │     3      7     11
  9.    4 │     4      8     12
  11. julia> list = [2,3]
  12. 2-element Vector{Int64}:
  13.  2
  14.  3
  16. julia> sum(df.x2[df.x1 .∈ Ref(list)])
  17. 13

此代码段使用了 Julia 中的广播功能，在其中 in（Julia 中的 ismember 函数）也可以写为 ∈。Ref(list) 用于防止对 list 进行广播。

英文:

One way could be:

  1. julia> df = DataFrame(reshape(1:12,4,3),:auto)
  2. 4×3 DataFrame
  3.  Row │ x1     x2     x3    
  4.      │ Int64  Int64  Int64 
  5. ─────┼─────────────────────
  6.    1 │     1      5      9
  7.    2 │     2      6     10
  8.    3 │     3      7     11
  9.    4 │     4      8     12
  11. julia> list = [2,3]
  12. 2-element Vector{Int64}:
  13.  2
  14.  3
  16. julia> sum(df.x2[df.x1 .∈ Ref(list)])
  17. 13

Uses broadcasting on in (how ismember is written in Julia) which can also be written as ∈. Ref(list) is used to prevent broadcasting over list.

答案2

得分: 1

filter! 是一个值得了解的函数，具体取决于你想要做什么（使用 Dan Getz 的代码示例）：

  1. julia> sum(filter!(:x1 => x1 -> x1 ∈ [2,3], df).x2)
  2. 13
英文:

Depending on what you want to do filter! is also worth knowing (using code form Dan Getz's answer):

  1. julia> sum(filter!(:x1 => x1 -> x1 ∈ [2,3], df).x2)
  2. 13

答案3

得分: 0

Not exactly sure if this is what you're asking but try intersect

  1. julia> using DataFrames
  3. julia> df = DataFrame(a = 1:5, b = 2:6)
  4. 5×2 DataFrame
  5.  Row │ a      b
  6.      │ Int64  Int64
  7. ─────┼──────────────
  8.    1 │     1      2
  9.    2 │     2      3
  10.    3 │     3      4
  11.    4 │     4      5
  12.    5 │     5      6
  14. julia> list = collect(3:10);
  16. julia> sum(df.b[intersect(df.a, list)])
  17. 15
英文:

Not exactly sure if this is what you're asking but try intersect

  1. julia> using DataFrames
  3. julia> df = DataFrame(a = 1:5, b = 2:6)
  4. 5×2 DataFrame
  5.  Row │ a      b
  6.      │ Int64  Int64
  7. ─────┼──────────────
  8.    1 │     1      2
  9.    2 │     2      3
  10.    3 │     3      4
  11.    4 │     4      5
  12.    5 │     5      6
  14. julia> list = collect(3:10);
  16. julia> sum(df.b[intersect(df.a, list)])
  17. 15

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  • 本文由 发表于 2023年2月14日 07:56:27
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  • arrays
  • dataframe
  • julia
  • sum
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