I'm working with a set of Fitbit data that I've downloaded and it has a list of weekdays that I'm trying to order properly. Now, the current data set has no "Fridays", but I want the factors to include it regardless.
How can I continue to factor the Weekdays, as 1-7 even if there are only 6 weekdays in the data set?
file<-choose.files()
slp<-data.frame(read.csv(file))
wkdaylevels<-c("Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday")
slp$FellAsleepAt<-strptime(slp$FellAsleepAt, format="%B %e, %Y at %I:%M%p")
slp$AwokeAt<-strptime(slp$AwokeAt,format="%B %e, %Y at %I:%M%p")
slp$TotalTimeSlept<-gsub("h ",":",slp$TotalTimeSlept)
slp$TotalTimeSlept<-gsub("m","",slp$TotalTimeSlept)
slp$TimeAsleep<-as.numeric(difftime(slp$AwokeAt,slp$FellAsleepAt))
slp$Date<-as.Date(slp$FellAsleepAt, format="%M/%D/%Y")
slp$DayofWeek<-as.factor(weekdays(slp$Date),levels=wkdaylevels)
ggplot(slp,aes(x=DayofWeek,y=TimeAsleep))+
geom_point()
Data here: https://docs.google.com/spreadsheets/d/1Vdgmtwx0vNKDKEZFMEGAWQ58H66ia-xjI0evR7idfkc/edit?usp=sharing
Answer: Use factor not as.factor
The function as coerces an object to a class. In your case, as.<type> coerces to a type (factor for you). The function factor is used to encode an object as a factor. The key difference is that as.factor does not allow a levels parameter, whereas factor does.
If you examine the source code of each function, you will see that as.factor does the coercion by using the unique levels of the object as its levels. factor does this if the levels= parameter is not specified, but allows the input of levels.
For example:
x <- 1:6
x2 <- factor(x, levels= 1:7)
levels(x2)
[1] "1" "2" "3" "4" "5" "6" "7"
x2 <- as.factor(x, levels= 1:7) # in this case, levels won't be evaluated due to lazy evaluation
Error in as.factor(x, levels = 1:7) : unused argument (levels = 1:7)
TBH, I'm not sure why your R session isn't giving you this error. Are you using R 3.2.3?