# dataframe_columns_impl

A dataframe whose value is a (column-wise) subset of another dataframes. The subset will be re-run as needed to reflect changes in the source dataframe; evaluation is lazy. The subset will be `eN["x_dataframe"][cols]`. Is a setting_user.

# set_df

    some_dfm set_df x_dataframe

Indicate that the source dataframe should be `eN["x_dataframe"]`.

Setting name: x

# set_columns

    some_dfn set_columns cols...

Indicate that `cols` are the required columns. Needs quotations marks around item(s); multiple items should be in `c()` format.

Setting name: x_column