Add a column with a constant value to a DataFrame
Solution 1:
To create such column:
df = DataFrame(x = 1:10, y = 'a':'j', d = 1)
To append such column to the existing DataFrame, you need broadcasting:
df.e .= 1
or
df[:, "f"] .= 1
Solution 2:
A more general alternative is:
julia> insertcols!(df, :z => 1)
10×3 DataFrame
Row │ x y z
│ Int64 Char Int64
─────┼────────────────────
1 │ 1 a 1
2 │ 2 b 1
3 │ 3 c 1
4 │ 4 d 1
5 │ 5 e 1
6 │ 6 f 1
7 │ 7 g 1
8 │ 8 h 1
9 │ 9 i 1
10 │ 10 j 1
which by default does the same, but it additionally:
- allows you to specify the location of the new column;
- by default makes sure that you do not accidentally overwrite an existing column