Julia数据框转化为矩阵
作者:互联网
Julia构建数据框
using DataFrames
t1 = DataFrame(y1=collect(1:3),y2=collect(4:6),y3=collect(7:9))
结果:
Main> t1 = DataFrame(y1=collect(1:3),y2=collect(4:6),y3=collect(7:9))
3×3 DataFrames.DataFrame
│ Row │ y1 │ y2 │ y3 │
├─────┼────┼────┼────┤
│ 1 │ 1 │ 4 │ 7 │
│ 2 │ 2 │ 5 │ 8 │
│ 3 │ 3 │ 6 │ 9 │
Julia构建矩阵
b = Array{Float64}(3,3)
b[:]=1:9
b
结果:
Main> b = Array{Float64}(3,3)
3×3 Array{Float64,2}:
5.06772e-316 1.15645e-315 1.15645e-315
1.15645e-315 1.15645e-315 1.15645e-315
1.15645e-315 1.15645e-315 5.06774e-316
Main> b[:]=1:9
1:9
Main> b
3×3 Array{Float64,2}:
1.0 4.0 7.0
2.0 5.0 8.0
3.0 6.0 9.0
对数据框进行矩阵操作, 报错
转置:
Main> t1'
ERROR: MethodError: no method matching transpose(::DataFrames.DataFrame)
Closest candidates are:
transpose(::BitArray{2}) at linalg\bitarray.jl:265
transpose(::Missings.Missing) at C:\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\JuliaPro-0.6.4.1\pkgs-0.6.4.1\v0.6\Missings\src\Missings.jl:92
transpose(::Number) at number.jl:113
...
Stacktrace:
[1] ctranspose(::DataFrames.DataFrame) at .\operators.jl:708
[2] eval(::Module, ::Any) at .\boot.jl:235
对矩阵进行操作, 成功
转置:
Main> b'
3×3 Array{Float64,2}:
1.0 2.0 3.0
4.0 5.0 6.0
7.0 8.0 9.0
编写函数将数据库转化为矩阵
思路:
- 提取数据框的行数和列数
- 定义相同行列的空数组
- 将相应的位置复制到数组中
function dataframe_2_array(dataframe)
(a,b)=size(dataframe)
A = Array{Float64}(a,b)
for i in 1:a
for j in 1:b
A[i,j] = dataframe[i,j]
end
end
return A
end
执行情况:
t2 = dataframe_2_array(t1)
t2
t2'
结果:
Main> t2 = dataframe_2_array(t1)
3×3 Array{Float64,2}:
1.0 4.0 7.0
2.0 5.0 8.0
3.0 6.0 9.0
Main> t2'
3×3 Array{Float64,2}:
1.0 2.0 3.0
4.0 5.0 6.0
7.0 8.0 9.0
标签:1.15645,Float64,矩阵,Julia,转化,dataframe,315,Array,Main 来源: https://blog.51cto.com/u_15242286/2842535