Interesting way to get r (correlation coefficient)

[bshoring]

The HP-55 was the first HP handheld to feature full six-register statistical accumulation. As best as I can tell, it wasn't until the HP-27 came out that this became standard.

Oddly, there is no "r" function on the 55. The manual does give a short method on page 61 of the manual to get r and r-squared:

f L.R.
Enter
g s (standard dev)
/
/ (this gives you r, though it is not mentioned in the book)
g x^2 (this gives you Coefficient of Determination)

On some calculators, you might have to insert an x<>y after L.R.

Since I don't own an HP-55, I tried it on an emulator for an HP-32E. With the x<>y after L.R. it works and this method for r perfectly matched the built in function.

Perhaps experts may be familiar with this method, but it was a new one to me.