急！R语言：找不到对象dat 请问如何修改 求问各位明白人

程序如下：library(quantmod)
library(minpack.lm)
startdate = "2020-01-01"
enddate = "2021-03-20"


sp500 <- new.env()
stkname="^GSPC"#"000001.SS" #
getSymbols(stkname, env = sp500, src = "yahoo",auto.assign=F,
           from = as.Date(startdate), to = as.Date(enddate))
?getSymbols


GSPC <- if (stkname=="^GSPC")sp500[["GSPC"]] else sp500[[stkname]]
rm(sp500)
dat<-dat[complete.cases(dat),]
dat<-GSPC[,4]
console窗口提示如下：

> dat<-dat[complete.cases(dat),]
错误: 找不到对象'dat