Finds the data frame index of a column from the name of the column or its index.
df.col.findId(df, label_name)a data frame in which to find the index of (a) specific column(s).
a character or numeric vector indicating the column name or index respectively.
an numeric vector corresponding to the column index that matches argument label_name.
This function allows the user to select one or several columns according to their name(s) or their index(es).