Julia: How to obtain the types of every column of a DataFrame/Table?

Question

There must be an easy way to obtain the column types of every column of a DataFrame. Currently, I do

using DataFrames
a = DataFrame(a = [1,2,3], str = ["a","b","c"], f = [0.0, 1.0, 5.0])
[eltype(Array(col)) for col in eachcol(a)]

Is the best way? Appreciate more efficient and elegant solutions

Answer 1

You can broadcast eltype over the columns of the data frame:

df = DataFrame(
    x = [1, 2, 3],
    y = ["a", "b", "c"],
    z = [0.0, 1.0, 5.0]
)

julia> eltype.(eachcol(df))
3-element Array{DataType,1}:
 Int64
 String
 Float64

Note: Older versions of DataFrames.jl had an eltypes function, but it has been deprecated and removed from the package.