def select_values_by_index(df, vector_row_pos, vector_col_pos):
    """Select values in the dataframe given specific indexes of rows and columns.
    
    Args:
        df (pd.DataFrame): Dataframe.
        vector_row_pos (array): Array of row positions.
        vector_col_pos (array): Array of column positions.
    
    Returns:
        pd.DataFrame: Dataframe with the specific values in the row and column indexes.
    
    Examples:
        >>> df = pd.DataFrame({"letters":["a","a","c"], "numbers":[1,2,3]})
        >>> select_values_by_index(df, vector_row_pos=[0,2], vector_col_pos=[0,1])
          letters  numbers
        0       a        1
        2       c        3
    """
    return df.iloc[vector_row_pos, vector_col_pos]