fit_merge函数的报错及疑问

不明白下面这个代码是什么意思

代码展示

fit
fit_merge
fit_merge<-fit
fit_merge[]<-0

c1
C1
C1<-c1
C1[]<-0

c2
C2
C2<-c2
C2[]<-0

c3
C3<-c3
C3[]<-0
C3

运行结果

fit
origin year Outbound_num tourits_num r.squared adj.r.squared sigma statistic p.value df logLik AIC BIC
1 Afghanistan tourits_num 24 58.06 0.965 0.9617 0.00661 289.6 0.000000000000000515 2 88.01 -168 -163.3
deviance df.residual nobs
1 0.0009175 21 24
fit_merge
origin year Outbound_num tourits_num r.squared adj.r.squared sigma statistic p.value df logLik AIC BIC deviance df.residual nobs
1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
fit_merge<-fit
fit_merge[]<-0
c1
Error: object 'c1' not found
C1
Error: object 'C1' not found
C1<-c1
Error: object 'c1' not found
C1[]<-0
Error in C1[] <- 0 : object 'C1' not found