Unknown HP Classic Prototype

[naddy]

(10-27-2024 11:34 AM)dm319 Wrote:  Having said that I don't know how linear regression, standard deviation etc are calculated on devices with limited memory.

Σ+ accumulates n, Σx, Σx², Σy, Σy², Σxy in registers. It follows that the available functions can be calculated from those values. Of course Thomas already provided the formulas.

The HP-42S additionally accumulates Σln x, Σ(ln x)², Σln y, Σ(ln y)², Σln x ln y, Σx ln y, Σy ln x, from which it can also provide exponential, logarithmic, and power curve fits. The HP-11C Owner's Handbook and Problem-Solving Guide has a curve-fitting program (p. 162ff), which builds the same functionality on top of the L.R. function by using the logarithm or exponential of various values, so there the curve fit must be chosen before data entry.