numobs(data)

Return the total number of observations contained in data.

If data does not have numobs defined, then in the case of Tables.table(data) == true returns the number of rows, otherwise returns length(data).

Authors of custom data containers should implement Base.length for their type instead of numobs. numobs should only be implemented for types where there is a difference between numobs and Base.length (such as multi-dimensional arrays).

getobs supports by default nested combinations of array, tuple, named tuples, and dictionaries.

See also getobs.

Examples

			
# named tuples 
x = (a = [1, 2, 3], b = rand(6, 3))
numobs(x) == 3

# dictionaries
x = Dict(:a => [1, 2, 3], :b => rand(6, 3))
numobs(x) == 3

All internal containers must have the same number of observations:

			julia> x = (a = [1, 2, 3, 4], b = rand(6, 3));

julia> numobs(x)
ERROR: DimensionMismatch: All data containers must have the same number of observations.
Stacktrace:
 [1] _check_numobs_error()
   @ MLUtils ~/.julia/dev/MLUtils/src/observation.jl:163
 [2] _check_numobs
   @ ~/.julia/dev/MLUtils/src/observation.jl:130 [inlined]
 [3] numobs(data::NamedTuple{(:a, :b), Tuple{Vector{Int64}, Matrix{Float64}}})
   @ MLUtils ~/.julia/dev/MLUtils/src/observation.jl:177
 [4] top-level scope
   @ REPL[35]:1