r - 错误： fct_collapse 中出现意外符号，库用于

Question

我正在使用此代码来组合这些级别

sal$type_employerCap = fct_collapse(sal$type_employer,
fed_loc_state = c(" Federal-gov","  Local-gov ","State-gov "),  
inc_not-inc_ prv = c("Private"," Self-emp-inc","Self-emp-not-inc") , 
? = c("Without-pay","Never-worked","?") ))

我的输出是：

错误：“sal$type_employerCap = fct_collapse(sal$type_employer,fed_loc_state = c(" Federal-gov"," Local-gov ","State-gov "), inc_not-inc_ prv" 中出现意外符号

看不懂，要改什么