Julia DataFrame: remove column by name

You can use select!:

julia> df = DataFrame(A = 1:4, B = ["M", "F", "F", "M"], C = 2:5)
4x3 DataFrame
|-------|---|-----|---|
| Row # | A | B   | C |
| 1     | 1 | "M" | 2 |
| 2     | 2 | "F" | 3 |
| 3     | 3 | "F" | 4 |
| 4     | 4 | "M" | 5 |

julia> select!(df, Not(:B))
4x2 DataFrame
|-------|---|---|
| Row # | A | C |
| 1     | 1 | 2 |
| 2     | 2 | 3 |
| 3     | 3 | 4 |
| 4     | 4 | 5 |

For more general ops, remember that you can pass an array of Symbols or a bool array too, and so arbitrarily complicated selections like

julia> df[~[(x in [:B, :C]) for x in names(df)]]
4x1 DataFrame
|-------|---|
| Row # | A |
| 1     | 1 |
| 2     | 2 |
| 3     | 3 |
| 4     | 4 |

julia> df[setdiff(names(df), [:C])]
4x1 DataFrame
|-------|---|
| Row # | A |
| 1     | 1 |
| 2     | 2 |
| 3     | 3 |
| 4     | 4 |

will also work.