用stata对变量取对数时遇到这样的问题,求大神解答
输入命令：gen ln mfincome1 =log( mfincome1 )
错误提示：[P]     error . . . . . . . . . . . . . . . . . . . . . . . .  Return code 110
        __________ already defined
        A variable or a value label has already been defined, and you
        attempted to redefine it.  This occurs most often with generate.
        If you really intend to replace the values, use replace.  If you
        intend to replace a value label, specify the replace option with
        the label define command.  If you are attempting to alter an
        existing label, specify the add or modify option with the
        label define command.