kindly help find out why the following code is given me error 


time<-c(80,80,90,90,85,85,85,85,85,85,92,77,85,85)
> tem<-c(170,180,170,180,175,175,175,175,175,175,175,175,182.07,167.93)
> yield<-c(80.5,81.5,82,83.5,83.9,84.3,84,79.7,79.8,79.5,78.4,75.6,78.6,77)
> Block<-c("B1","B1","B1","B1","B1","B1","B1","B2","B2","B2","B2","B2","B2","B2")
> chem<-data.frame(time,tem,Block,yield)
> ggg<-coded.data(chem, x1 ~ (time - 85)/5, x2 ~ (tem - 175)/5)
> gg1=rsm(yield~ FO(x1,x2),data=chem,subset = (Block == "B1"))
Error in lapply(X = X, FUN = FUN, ...) : object 'x1' not found
> gg1=rsm(yield~ SO(x1,x2),data=chem,subset = (Block == "B1"))
Error in lapply(X = X, FUN = FUN, ...) : object 'x1' not found

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