could not find function "ndiffs"

The "ndiffs" function is part of the "forecast" package in R. To use it, you need to first install and load the package by running the following commands:

install.packages("forecast")
library(forecast)

After loading the package, you should be able to use the "ndiffs" function. If you still encounter the error message "could not find function", it is possible that the package was not installed correctly or that your R environment is not properly configured. In this case, you may need to reinstall the package or troubleshoot your R installation.