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Add nrow and ncol #285

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Add nrow and ncol #285

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2ff4a60
Add `columncount`
rikhuijzer Jun 29, 2022
ccf71e0
Rename to `nrow` and `ncol`
rikhuijzer Jun 29, 2022
27c4c48
Apply suggestions from code review
rikhuijzer Jun 30, 2022
5722256
Define nrow and ncol more selectively
rikhuijzer Jun 30, 2022
30ee986
Change to minor version bump
rikhuijzer Jun 30, 2022
ca81386
Rename ncols to ncol
rikhuijzer Jun 30, 2022
f094263
Align table again
rikhuijzer Jun 30, 2022
acc8ac8
Small change
rikhuijzer Jul 4, 2022
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2 changes: 1 addition & 1 deletion Project.toml
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
name = "Tables"
uuid = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
authors = ["quinnj <[email protected]>"]
version = "1.7.0"
version = "1.7.1"

[deps]
DataAPI = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"
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3 changes: 1 addition & 2 deletions src/Tables.jl
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Expand Up @@ -208,8 +208,7 @@ function Base.show(io::IO, x::T) where {T <: AbstractRow}
end

function Base.show(io::IO, table::AbstractColumns; max_cols = 20)
ncols = length(columnnames(table))
print(io, "$(typeof(table)) with $(rowcount(table)) rows, $(ncols) columns, and ")
print(io, "$(typeof(table)) with $(nrow(table)) rows, $(ncol(table)) columns, and ")
sch = schema(table)
if sch !== nothing
print(io, "schema:\n")
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10 changes: 7 additions & 3 deletions src/fallbacks.jl
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Expand Up @@ -4,12 +4,16 @@

# Turn any AbstractColumns into an AbstractRow iterator

# get the number of rows in the incoming table
function rowcount(cols)
"Return the number of rows in the incoming table."
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function nrow(cols)
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@bkamins, does this not pirate a default definition? I'm a little uncomfortable with this definition because technically rowcount was only meant to be called on the result of Tables.columns, but now it "looks like" it works generically on any table. And for the most part, it probably will, but we're not really following the principles of the interface.

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does this not pirate a default definition?

DataAPI.jl does not define any method for this function. Same for ncol - DataAPI.jl does not define any method for this function.

As I have commented - it does pirate as it add the definition to ncol with ::Any signature. The problem is exactly what you have commented - some tables might not have a well defined row count (maybe also the same problem is for ncol). So what do you think would be best to do? What I would ideally have is some definition that works by default correctly. I think that if default errors it is not a huge problem if it does not error on "standard" tables.

Maybe what we should do is:

  • leave rowcount to be internal;
  • define nrow and ncol only for tables defined in Tables.jl tables (rowtable, coltable, dictrowtable, dictcolumntable, table maybe some more? - you know best)

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Yes, that's what I would prefer (only define for Tables.jl-defined tables. I'm also happy to add recommendations to the docs that table types should strongly consider implementing nrow/ncol on their own table types as apart of the API.

names = columnnames(cols)
isempty(names) && return 0
return length(getcolumn(cols, names[1]))
end
@deprecate rowcount(x) nrow(x)

"Return the number of columns in the incoming table."
ncol(cols) = length(columnnames(cols))
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Same here; columnnames and getcolumn are only technically allowed to be called on the result of Tables.columns or on individual iterated rows from Tables.rows, so this makes me a bit uncomfortable.


# a lazy row view into a AbstractColumns object
struct ColumnsRow{T} <: AbstractRow
Expand Down Expand Up @@ -86,7 +90,7 @@ function rows(x::T) where {T}
# first check if it supports column access, and if so, wrap it in a RowIterator
if columnaccess(x)
cols = columns(x)
return RowIterator(cols, Int(rowcount(cols)))
return RowIterator(cols, Int(nrow(cols)))
# otherwise, if the input is at least iterable, we'll wrap it in an IteratorWrapper
# which will iterate the input, validating that elements support the AbstractRow interface
# and unwrapping any DataValues that are encountered
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2 changes: 1 addition & 1 deletion src/matrix.jl
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Expand Up @@ -84,7 +84,7 @@ function matrix(table; transpose::Bool=false)
cols = Columns(table)
types = schema(cols).types
T = reduce(promote_type, types)
n, p = rowcount(cols), length(types)
n, p = nrow(cols), length(types)
if !transpose
matrix = Matrix{T}(undef, n, p)
for (i, col) in enumerate(cols)
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2 changes: 1 addition & 1 deletion src/namedtuples.jl
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Expand Up @@ -108,7 +108,7 @@ end

# NamedTuple of arrays of matching dimensionality
const ColumnTable = NamedTuple{names, T} where {names, T <: NTuple{N, AbstractArray{S, D} where S}} where {N, D}
rowcount(c::ColumnTable) = length(c) == 0 ? 0 : length(c[1])
nrow(c::ColumnTable) = length(c) == 0 ? 0 : length(c[1])

# interface implementation
istable(::Type{<:ColumnTable}) = true
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4 changes: 3 additions & 1 deletion test/runtests.jl
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Expand Up @@ -132,7 +132,9 @@ end

rt = [(a=1, b=4.0, c="7"), (a=2, b=5.0, c="8"), (a=3, b=6.0, c="9")]
nt = (a=[1,2,3], b=[4.0, 5.0, 6.0], c=["7", "8", "9"])
@test Tables.rowcount(nt) == 3
@test_deprecated Tables.rowcount(nt)
@test Tables.nrow(nt) == 3
@test Tables.ncol(nt) == 3
@test Tables.schema(nt) == Tables.Schema((:a, :b, :c), Tuple{Int, Float64, String})
@test Tables.istable(typeof(nt))
@test Tables.columnaccess(typeof(nt))
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