As far as I can tell, the plot.ACF function was never exported. The earliest version of nlme from https://cran.r-project.org/src/contrib/Archive/nlme/ that I could find with a NAMESPACE file was nlme_3.1-40 (Date: 2003-05-16), and that function would have been invisible (at the console). It still would have been accessible with the methods
function and the code would have been available with the triple dot mechanism (:::
) or getAnywhere
functions.
getAnywhere("plot.ACF") Retruns formal parameters, funciton body and information about functions environment
getS3method("plot", "ACF") # returns same code as getAnywhere
x <- methods(class="ACF")
str(x)
#--------------
'MethodsFunction' chr "plot.ACF"
- attr(*, "info")='data.frame': 1 obs. of 4 variables:
..$ visible: logi FALSE
..$ from : Factor w/ 1 level "registered S3method": 1
..$ generic: chr "plot"
..$ isS4 : logi FALSE
- attr(*, "byclass")= logi TRUE
I apologize for my earlier, somewhat snarky comment, because on re-reading your post it appears you do understand that the functions is available, just not visible. What's still unclear is why you thought it was ever visible.
If you want to have plot.ACF exported, you could add it to the list of exported functions in the NAMESPACE file and rebuild the package. Or you could export on the fly with:
plot.ACF <- getAnywhere("plot.ACF")