My question is what is a symbol as in the following warning message?
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julia> df = DataFrame(A = 1:10, B = 2:2:20)
10x2 DataFrame
|-------|----|----|
| Row # | A | B |
| 1 | 1 | 2 |
| 2 | 2 | 4 |
| 3 | 3 | 6 |
| 4 | 4 | 8 |
| 5 | 5 | 10 |
| 6 | 6 | 12 |
| 7 | 7 | 14 |
| 8 | 8 | 16 |
| 9 | 9 | 18 |
| 10 | 10 | 20 |
julia> julia> df["A"]
WARNING: indexing DataFrames with strings is deprecated; use symbols instead
in depwarn at deprecated.jl:36
in getindex at ~/.julia/DataFrames/src/deprecated.jl:107
10-element DataArray{Int64,1}:
1
2
3
4
5
6
7
8
9
10
