Why does the table function find a variable that was deleted?
Dog <- c("Rover", "Spot")
Cat <- c("Scratch", "Fluffy")
Pets <- data.frame(Dog, Cat) #create a data frame with two variables
names(Pets)
# [1] "Dog" "Cat"
#rename Dog to a longer name
names(Pets)[names(Pets)=="Dog"] <- "Dog_as_very_long_name"
Pets$Dog <- NULL # delete Dog
names(Pets)
#[1] "Dog_as_very_long_name" "Cat" #the variable dog is not in the data set anymore
table(Pets$Dog) #Why does the table function on a variable that was deleted
# Rover Spot
# 1 1
This is simply because of the partial matching that occurs in certain uses of $
.
Try this:
> table(Pets$Ca)
Fluffy Scratch
1 1
Using the [[
notation instead will give you more control.
> table(Pets[["Ca"]])
< table of extent 0 >
> table(Pets[["Ca", exact = FALSE]])
Fluffy Scratch
1 1
You can use the options
settings to give a warning when partial matches are used. Consider:
> options(warnPartialMatchDollar = TRUE)
> table(Pets$Ca)
Fluffy Scratch
1 1
Warning message:
In Pets$Ca : partial match of 'Ca' to 'Cat'
> table(Pets$Dog)
Rover Spot
1 1
Warning message:
In Pets$Dog : partial match of 'Dog' to 'Dog_as_very_long_name'
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