@gung recently created the acf-pcf tag which now has 9 questions: 2 old threads tagged by @gung and 7 new threads (plus 1 migrated to SO). I have two questions about the tag:
- Do we need it?
If we need it, can we at least replace
pacfin the tag name?
Edit: 2. Has been done already, only 1. remains relevant.
Regarding 1., I think we were doing more or less OK without it. Most of the questions containing ACF and/or PACF I have encountered on CV would ask for
- identifying an ARIMA structure from ACF/PACF where autocorrelation, arima and model-selection tags are sufficient (IMHO) or
- diagnosing problems with a model when some autocorrelation is found in model residuals; there autocorrelation and diagnostic are sufficient (IMHO).
If we were to get rid of the tag, it could be
- made a synonym of autocorrelation or
- just replaced by the above-mentioned tags in the few threads tagged with acf-pcf but not the ones above, and deleted in other.
Regarding 2., PACF is the standard acronym of partial autocorrelation function in time series econometrics, while I cannot remember seeing PCF before (though I would not be surprised it exists). On Cross Validated, PACF can be encoutered 670 times while PCF only 17 times. I think having PCF in place of PACF in a tag name may be confusing and may spread the unwarranted use of the nonstandard acronym (so that instead of searching for PACF one will now have to search for both PACF and PCF to capture all the relevant posts).
acf-pacf) or make it a synonym, and then the intuitive synonym for me is indeed autocorrelation. $\endgroup$