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+--- Thread: HP-25 statistics weirdness (/thread-20609.html)
HP-25 statistics weirdness - John Garza (3665) - 10-09-2023 12:27 PM
Ever notice the HP-25 does not accumulate the y^2 value in a stat register? Makes things like computing r^2 for linear regression a chore as you have to account for it in your code on data entry. Also, RCL Sigma+ is not allowed - making our fearless pilot Mr. Sweeny hit a couple of extra keys - not to mention having to remember where SigmaX and SigmaY are stored.
Doing a little research, I found the HP-25 is unique in this. It's predecessor, the HP-55 has both y^2 and RCL Sigma+, and so does it's successors, the HP29C and the HP-33E/C. The HP-27 has y^2 but lacks RCL Sigma+.
I presume all this weirdness is due to space imitations? And yet the 25 has percentage and NOP ?
-J
RE: HP-25 statistics weirdness - Thomas Klemm - 10-09-2023 08:37 PM
I could imagine that \(\sum y\) and \(\sum xy\) can still be useful in case of a frequency table.
You can interpret \(y\) as frequency and \(x\) as value.
The mean is then:
\(
\bar{x} = \frac{\sum xy}{\sum y}
\)
Example:
\(
\begin{array}{|c|c|}
\hline
Frequency & Value \\
\hline
3 & 7 \\
5 & 11 \\
2 & 13 \\
\hline
\end{array}
\)
CLEAR REG
3 ENTER 7 \(\Sigma +\)
5 ENTER 11 \(\Sigma +\)
2 ENTER 13 \(\Sigma +\)
RCL 5
RCL 4
\(\div\)
10.20
RE: HP-25 statistics weirdness - John Garza (3665) - 10-09-2023 09:31 PM
BTW,
How did you get the sigma symbols to display in your post?
I looked and could not find that in the editor.
-J
RE: HP-25 statistics weirdness - Thomas Klemm - 10-09-2023 11:50 PM
You can hit the
![[Image: postbit_quote.gif]](https://hpmuseum.org/forum/images/english/postbit_quote.gif)
button on any post to see the code.In this case it is embedded LaTeX, or specifically \sum for the \(\sum\) sign.
Or then \Sigma + for \(\Sigma +\).
RE: HP-25 statistics weirdness - Steve Simpkin - 10-10-2023 01:18 AM
(10-09-2023 12:27 PM)John Garza (3665) Wrote: Ever notice the HP-25 does not accumulate the y^2 value in a stat register? Makes things like computing r^2 for linear regression a chore as you have to account for it in your code on data entry. Also, RCL Sigma+ is not allowed - making our fearless pilot Mr. Sweeny hit a couple of extra keys - not to mention having to remember where SigmaX and SigmaY are stored.
Doing a little research, I found the HP-25 is unique in this. It's predecessor, the HP-55 has both y^2 and RCL Sigma+, and so does it's successors, the HP29C and the HP-33E/C. The HP-27 has y^2 but lacks RCL Sigma+.
I presume all this weirdness is due to space imitations? And yet the 25 has percentage and NOP ?
-J
I believe you are correct about why that feature was not included. As William C Wickes has said on other HP calculator projects when asked why a feature was missing from a particular model, "Life is short and ROM is full". In the case of the HP-25, this is literally true. There was no room left in the HP-25's ROM to add *any* feature unless you removed a feature or were able to further optimize the code to make more room.
https://www.hpmuseum.org/forum/thread-8536-post-74865.html#pid74865
I suspect they put a higher priority on the percentage and NOP functions than on accumulating the y^2 value in a statistics register. Considering the HP-25 didn't start out as a programmable calculator, I think they did an amazing job including the features they did in the very limited ROM space they had available.