Create an empty data.frame first and then give values to it by accessing the index value.
#Creating an empty datda.frame with 100 rows and 2 columns
My_Data<- data.frame(Numbers=rep(NA, 100), Names=rep("", 100),stringsAsFactors=FALSE)
#Now, go ahead and start giving the values by accesing the index value like this:
My_Data[i, ] <- list(10.7, "Spartaa!")