Question

如何在IndexedTable中添加或编辑值？从the documentation中，我了解到IndexedTable对象本身是不可变的，但不是底层数据，因此我“理解”了为什么这样的方法不起作用，但是我不知道如何使用新数据获取新的IndexedTable ：

myTable = ndsparse((
             region      = ["US","US","US","US","EU","EU","EU","EU"],
             product     = ["apple","apple","banana","banana","apple","apple","banana","banana"],
             year        = [2011,2010,2011,2010,2011,2010,2011,2010]
           ),(
             production  = [3.3,3.2,2.3,2.1,2.7,2.8,1.5,1.3],
             consumption = [4.3,7.4,2.5,9.8,3.2,4.3,6.5,3.0]
          ))
myTable["EU","banana",2011] = (2.5, 7.5) # ERROR: type Tuple has no field region
myTable["EU","banana",2012] = (2.5, 7.5) # ERROR: type Tuple has no field region
myTable["EU","banana",2011] = (production = 2.5, consumption = 7.5) # ERROR: type Tuple has no field region

Answer 1

您想要的功能似乎在JuliaDB的Base.merge下。

merge(a::NDSparse, a::NDSparse; agg)

将a的行与b的行合并。要保留唯一键，b中的值优先。提供的函数agg将汇总来自和b具有相同的密钥。
Example:

a = table((x = 1:5, y = rand(5)); pkey = :x)
b = table((x = 6:10, y = rand(5)); pkey = :x)
merge(a, b)

a = ndsparse([1,3,5], [1,2,3])
b = ndsparse([2,3,4], [4,5,6])
merge(a, b)
merge(a, b; agg = (x,y) -> x)

基于您的问题的工作示例：

# tested on Julia 1.0.4
julia> using JuliaDB
julia> myTable = ndsparse((
                    region      = ["US","US","US","US","EU","EU","EU","EU"],
                    product     = ["apple","apple","banana","banana","apple","apple","banana","banana"],
                    year        = [2011,2010,2011,2010,2011,2010,2011,2010]
                  ),(
                    production  = [3.3,3.2,2.3,2.1,2.7,2.8,1.5,1.3],
                    consumption = [4.3,7.4,2.5,9.8,3.2,4.3,6.5,3.0]
                 ))
3-d NDSparse with 8 values (2 field named tuples):
region  product   year │ production  consumption
───────────────────────┼────────────────────────
"EU"    "apple"   2010 │ 2.8         4.3
"EU"    "apple"   2011 │ 2.7         3.2
"EU"    "banana"  2010 │ 1.3         3.0
"EU"    "banana"  2011 │ 1.5         6.5 # Note the old value
"US"    "apple"   2010 │ 3.2         7.4
"US"    "apple"   2011 │ 3.3         4.3
"US"    "banana"  2010 │ 2.1         9.8
"US"    "banana"  2011 │ 2.3         2.5

julia> updated_myTable = ndsparse((
                    region      = ["EU"],
                    product     = ["banana"],
                    year        = [2011]
                  ),(
                    production  = [2.5], # new values here
                    consumption = [7.5]
                 ))
3-d NDSparse with 1 values (2 field named tuples):
region  product   year │ production  consumption
───────────────────────┼────────────────────────
"EU"    "banana"  2011 │ 2.5         7.5

julia> newTable = merge(updated_myTable, myTable, agg = (x,y) -> x)
3-d NDSparse with 8 values (2 field named tuples):
region  product   year │ production  consumption
───────────────────────┼────────────────────────
"EU"    "apple"   2010 │ 2.8         4.3
"EU"    "apple"   2011 │ 2.7         3.2
"EU"    "banana"  2010 │ 1.3         3.0
"EU"    "banana"  2011 │ 2.5         7.5 # Note the updated values here!
"US"    "apple"   2010 │ 3.2         7.4
"US"    "apple"   2011 │ 3.3         4.3
"US"    "banana"  2010 │ 2.1         9.8
"US"    "banana"  2011 │ 2.3         2.5

请注意，agg函数在遇到冲突时如何偏爱第一个参数中的键。

另一种骇人听闻的方法是在找到正确的索引后直接编辑数据元素。

julia> i = findfirst(isequal((region = "EU", product = "banana", year = 2011)), myTable.index)
4

julia> myTable.data[i]
(production = 1.5, consumption = 6.5)

julia> myTable.data[i] = (production = 2.5, consumption = 7.5)
(production = 2.5, consumption = 7.5)

julia> myTable
3-d NDSparse with 8 values (2 field named tuples):
region  product   year │ production  consumption
───────────────────────┼────────────────────────
"EU"    "apple"   2010 │ 2.8         4.3
"EU"    "apple"   2011 │ 2.7         3.2
"EU"    "banana"  2010 │ 1.3         3.0
"EU"    "banana"  2011 │ 2.5         7.5 # Note the updated values here!
"US"    "apple"   2010 │ 3.2         7.4
"US"    "apple"   2011 │ 3.3         4.3
"US"    "banana"  2010 │ 2.1         9.8
"US"    "banana"  2011 │ 2.3         2.5

希望有帮助。

如何在IndexedTable中添加/编辑值？

1 个答案: