楼主在进行非线性回归，因为expression too long引起问题，所以楼主转用了nl的function evaluator program（FEP）功能。
但是FEP现在出现一个r(111)的问题，具体报错信息就只有如下
nlcombination returned 111
verify that nlcombination is a function evaluator program

我也在google中查找了基本上所有关于这个问题的解答也还是找不出答案，所以请教下这种具体报错信息只有两句，没有具体问题的错误怎么解决。下面是r(111)的问题解释，我一一对应着找了，不存在变量没有定义以及merge或者缩写的问题，至于variable out of order我的varlist中也没有varname1-varname2的定义，所以有碰到相同问题的朋友吗，或者某位大神帮忙解答下


r(111)“ error . . . . . . . . . . . . . . . . . . . . . . . .  Return code 111
        __________ not found;
        no variables defined;
        The variable does not exist.  You may have mistyped the
        variable's name.
        variables out of order;
        You specified a varlist containing varname1-varname2, yet
        varname1 occurs after varname2.  Reverse the order of the
        variables if you did not make some other typographical error.
        Remember, varname1-varname2 is taken by Stata to mean varname1,
        varname2, and all the variables in dataset order in between.
        Type describe to see the order of the variables in your dataset.
        __________ not found in using data;
        You specified a varlist with merge, but the variables on which
        you wish to merge are not found in the using dataset, so the
        merge is not possible.
        __________ ambiguous abbreviation;
        You typed an ambiguous abbreviation for a variable in your data.
        The abbreviation could refer to more than one variable.  Use a
        nonambiguous abbreviation, or if you intend all the variables
        implied by the ambiguous abbreviation, append a `*' to the end
        of the abbreviation.”