Dx.Elem<-list(c("DX1", "DX2", "DX3", "DX4", "DX5", "DX6", "DX7", "DX8", "DX9", "DX10", "DX11", "DX12", "DX13", "DX14", "DX15", "DX16", "DX17", "DX18",
              "DX19", "DX20", "DX21", "DX22", "DX23", "DX24", "DX25"))

Dx.Panc9<-list("86384", "86394", "86382", "86392", "86381", "86391", "86383", "86393")

mydata2$Panc9<-0
mydata2$Panc9[mydata2$DX1 %in% Dx.Panc9]<-1
mydata2$Panc9[mydata2$DX2 %in% Dx.Panc9]<-1
mydata2$Panc9[mydata2$DX3 %in% Dx.Panc9]<-1
mydata2$Panc9[mydata2$DX4 %in% Dx.Panc9]<-1

mydata2$Panc9[mydata2[, Dx.Elem] %in% Dx.Panc9]<-1

Error in .subset(x, j) : invalid subscript type 'list'