How to check if a variable is defined in R without getting an error?

Question

I tried this, which failed

is.na(ppcc) Error: object 'ppcc' not found

is.finite(ppcc) Error: object 'ppcc' not found

Answer 1

You can try exists():

exists("Unknown Value")    

[1] FALSE

Unknown Value <- 42

exists("Unknown value")

[1] TRUE

Or you can also do it using data a frame method:

Let's create a data frame first :

data <- data.frame(z1 = c(2, 8, 8, 1, 1), # Create example data.frame

                  z2 = c(6, 7, 1, 3, 1))   //We are creating 2 data frames

If there's a need to check for the existence of particular column names in the data frame above we need to attach the data frame first using:

attach(data)    # This will Attach data.frame

and after this check the existence of variable names in the data, using:

exists("z1")                              # Apply exists to variable of data

# TRUE

z1 exists:

exists("z3")        # Apply exists to non-existent variable

# FALSE

but Z3 doesn't exist.

after this detach the data as it can lead to confusion in the following programming steps:

detach(data)               # This will Detach data.frame

Happy Learning...!!