add sum of squares (ss) as a function

[jiyunson]

Hi, big fan of this package. I use it to teach and I'd like students to be able to use a similar syntax to quickly look at SS versus MSE or RMSE. Would you be able to add this function to your package?

ss <- function(actual, predicted){sum((actual-predicted)^2)}

It's not so much for actual research but it would be nice from a teaching perspective! Thank you for considering.

[jiyunson]

Ah, disregard my request. I just found sse() which is exactly what I needed. I had trouble finding it initially because it wasn't on the list of Metrics on this page: https://github.com/mfrasco/Metrics

Thanks!