Further performance metrics to add

[strengejacke]

This would definitely fit.

Other things that come to my mind when I think of the scope:

• Other indices used in the structural equation field (this bunch of guys). As they are computed by default by lavaan, it would mostly consist of extractors consistent with the easyverse.
• Convenience methods for PCAs / Factor Analysis, returning the % of variance explained.
• I think that in general, and in the future, the easyverse (that is a thing now :) methods could be useful in the machine learning world, where people struggle with different models/packages. Providing a unifying syntax for extracting, interpreting and understanding their models could be quite appreciated. Although this will probably wait for the help of a future contributor, expert in this kind of things. But providing the tools to bridge the regression world with the ML world could be quite cool.

Originally posted by @DominiqueMakowski in #14 (comment)

[strengejacke]

All the *_performance functions computes in-sample based measures. From my point of view the word "performance" suggests how well the model works
out-of-sample. Would it be possible to add out-of-sample measures like RMSE, MAE, out-of-sample R^2, and for classification: AUC, precision, recall +++

[bwiernik]

I have formulas for all of the SEM fit indices under the sun. I can take that.

[bwiernik]

Regarding out of sample stuff, I would also love if performance could do various true cross-validation stuff, both individual residuals and aggregates like RMSE, R^2^, and deviance. Those are currently strewn across various packages.

[bwiernik]

Regarding PCA/factor analysis, to meet most user expectations, that's going to require at least a handful of dependencies like GPArotation. Various nuances of rotations and extraction methods are pretty fiddly, but also already well-implemented in psych and fungible. I would suggest these functions should be wrappers, probably starting with the princomp, factanal, and psych::fa() and psych::fa.parallel() functions.

[bwiernik]

Providing a unifying syntax for extracting, interpreting and understanding their models could be quite appreciated. Although this will probably wait for the help of a future contributor, expert in this kind of things.

Isn't that essentially the aim of tidymodels?