Tables and DataFrames

Tables.jl provides an ecosystem-wide interface to tabular data in julia, giving interop with DataFrames.jl, CSV.jl and hundreds of other packages that implement the standard.

DimensionalData.jl implements the Tables.jl interface for AbstractDimArray and AbstractDimStack. DimStack layers are unrolled so they are all the same size, and dimensions loop to match the length of the largest layer.

Columns are given the name or the array or the stack layer key. Dimension columns use the Symbol version (the result of DD.dim2key(dimension)).

Looping of dimensions and stack layers is done lazily, and does not allocate unless collected.

Example

using DimensionalData, Dates, DataFrames

Define some dimensions:

julia> x, y, c = X(1:10), Y(1:10), Dim{:category}('a':'z')

↓ X        1:10,
→ Y        1:10,
↗ category 'a':1:'z'

julia> A = rand(x, y, c; name=:data)

╭───────────────────────────────────╮
│ 10×10×26 DimArray{Float64,3} data │
├───────────────────────────────────┴───────────────────── dims ┐
  ↓ X        Sampled{Int64} 1:10 ForwardOrdered Regular Points,
  → Y        Sampled{Int64} 1:10 ForwardOrdered Regular Points,
  ↗ category Categorical{Char} 'a':1:'z' ForwardOrdered
└───────────────────────────────────────────────────────────────┘
[:, :, 1]
  ↓ →  1          2         3          …  8          9          10
  1    0.98923    0.494425  0.0485103     0.591008   0.695832    0.0954375
  2    0.132046   0.172035  0.988767      0.425177   0.521827    0.681577
  3    0.811807   0.898238  0.835698      0.703425   0.0857436   0.137483
  4    0.986466   0.962102  0.536363      0.0118509  0.5543      0.0438266
  ⋮                                    ⋱                         ⋮
  7    0.132927   0.62582   0.270968      0.701969   0.671722    0.105779
  8    0.659444   0.696955  0.955354      0.215741   0.112198    0.734391
  9    0.541292   0.756739  0.243488      0.21418    0.465607    0.231252
 10    0.0443724  0.650058  0.396104   …  0.770442   0.923159    0.475621

Converting to DataFrame

Arrays will have columns for each dimension, and only one data column

julia> DataFrame(A)

2600×4 DataFrame
  Row │ X      Y      category  data
      │ Int64  Int64  Char      Float64
──────┼───────────────────────────────────
    1 │     1      1  a         0.98923
    2 │     2      1  a         0.132046
    3 │     3      1  a         0.811807
    4 │     4      1  a         0.986466
    5 │     5      1  a         0.822923
    6 │     6      1  a         0.17712
    7 │     7      1  a         0.132927
    8 │     8      1  a         0.659444
  ⋮   │   ⋮      ⋮       ⋮          ⋮
 2594 │     4     10  z         0.451226
 2595 │     5     10  z         0.320397
 2596 │     6     10  z         0.828402
 2597 │     7     10  z         0.942326
 2598 │     8     10  z         0.259623
 2599 │     9     10  z         0.720341
 2600 │    10     10  z         0.69682
                         2585 rows omitted

Converting to CSV

We can also write arrays and stacks directly to CSV.jl, or any other data type supporting the Tables.jl interface.

julia> using CSV

julia> CSV.write("dimstack.csv", st)

"dimstack.csv"

julia> readlines("dimstack.csv")

2601-element Vector{String}:
 "X,Y,category,data1,data2"
 "1,1,a,0.8925456476827067,0.6754285497685953"
 "2,1,a,0.08453433283655587,0.9364272097621991"
 "3,1,a,0.009117443658263502,0.34716916927339125"
 "4,1,a,0.3429860397050317,0.029231223586021038"
 "5,1,a,0.661849081229783,0.17185101336631825"
 "6,1,a,0.39187220290678226,0.4714168586103352"
 "7,1,a,0.029191993104933922,0.947654384327241"
 "8,1,a,0.7089801287974157,0.1526833034766708"
 "9,1,a,0.3752691165022767,0.17700228416642227"
 ⋮
 "2,10,z,0.6393587977015998,0.04353900096422991"
 "3,10,z,0.6746507486667644,0.5261597289524632"
 "4,10,z,0.01090262641691575,0.20515070331860819"
 "5,10,z,0.29450159501715556,0.8854894267628785"
 "6,10,z,0.7133255046656136,0.7042215164956682"
 "7,10,z,0.9272611825896064,0.17036100971286572"
 "8,10,z,0.9388715092143414,0.2797753964779216"
 "9,10,z,0.8375022559753681,0.25497854880545423"
 "10,10,z,0.8236655973126321,0.06645252184044714"