could not find function "adf.test"

The error message "could not find function 'adf.test'" means that the R interpreter cannot find the function "adf.test" in any loaded packages.

This error can occur if the package containing the function has not been installed or loaded. To solve this error, you need to install and load the appropriate package that contains the 'adf.test' function.

For example, if you want to use the 'adf.test' function from the 'tseries' package, you can install and load the package using the following R code:

install.packages("tseries")
library(tseries)

After you have loaded the 'tseries' package, you should be able to use the 'adf.test' function without encountering the "could not find function 'adf.test'" error.