The warning message is because your “Type” variable was made a factor and “lunch” was not a defined level. Use the stringsAsFactors = FALSE flag when making your data frame to force “Type” to be a character.
> fixed <- data.frame("Type" = character(3), "Amount" = numeric(3))
> str(fixed)
‘data.frame’: 3 obs. of 2 variables:
$ Type : Factor w/ 1 level “”: NA 1 1
$ Amount: chr “100” “0” “0”
>
> fixed <- data.frame("Type" = character(3), "Amount" = numeric(3),stringsAsFactors=FALSE)
> fixed[1, ] <- c("lunch", 100)
> str(fixed)
‘data.frame’: 3 obs. of 2 variables:
$ Type : chr “lunch” “” “”
$ Amount: chr “100” “0” “0”
If you are reading directly from CSV file then do like this.
myDataFrame <- read.csv("path/to/file.csv", header = TRUE, stringsAsFactors = FALSE)