|Re: wp34s - New Release|
Message #12 Posted by Dieter on 24 Mar 2011, 4:17 p.m.,
in response to message #1 by Marcus von Cube, Germany
Ah, great - it's LOGxY again. :-)
Both in this and in earlier releases I noticed some details I would like to mention.
- At several occasions the emulator simply disappeared from the screen and did not come back - although it was still active and its icon was visible in the task bar. Start WP34s, switch to another program (e.g. Notepad), try to switch back to WP34s - and nothings happens. The only way to resolve this: close the program and restart it. OS: Windows XP SP3.
- After the emulator has been switched to "hide titlebar" there is no way to move it across the screen. The user has to turn the titlebar on, move the program window and hide the titlebar again. I think the usual keyboard shortcuts like Alt+Space (Windows) should work even with the titlebar turned off.
- A right-click anywhere on the calculator surface works like pressing the f prefix. Is this a bug of a hidden feature?
- While a program is running the display shows the x-register, not something like "running", like other HPs. The only thing that hints at a running program is a tiny flashing "RCL" in the upper right corner. BTW, I would prefer something moving across the display, like... a running chicken, a swimming duck, ...you get the idea. ;-)
- VIEW is not working (edit: not SHOW, as originally stated). At least it's not working the way I'd expect. Try this short example:
001 LBL B
004 STO 01
005 LBL 01
006 VIEW 01
008 DSZ 01 ; aaah, finally DSZ is back. :-)
009 GTO 01
Instead of the expected countdown the display shows nothing but a "10" (or simply X, if interrupted and restarted) and a flashing RCL-announciator - for the whole ten seconds the program is running.
- -123 mod 5 gives -3 on the 34s. My other HPs with MOD or RMDR function return 2. I assume that's also true for the 42s which the manual refers to regarding this function.
- The normal CDF now is more precise, but full machine precision is not achieved. Especially in the tails (x >= 2) this could be done easily with a simple continued fraction expansion. Unoptimized pseudo-code:
n := 4 + 100 div (x-1) ; see below
s := 1/n
for c := n-1 downto 1 do
s := c / (s + x)
s := s + x
cdf := pdf(x) / s
I tried to determine a rule for the number of terms n, depending on x and the desired accuracy (d digits). As far as I can tell on a system working with usual binary double precision numbers (15-16 valid decimals) this value can be estimated for d = 8...16 digits quite exactly by
k >= 17 + d * (d-5) / 2 (the example uses k = 100 for d ~= 16)
n >= 4 + int(k / (x-1))
This should return the value for s with d valid digits and an error near 0,2 ULP. With 39 internal digits on the 34s the desired 16-digit result can be evaluated without effort, since the required pdf and its exp(-0,5*x^2) can be evaluated with sufficient precision. All this is calculated in virtually no time.
- While we're on this topic: the common use of the symbols P and Q for the cumulative normal distribution is P for the lower tail and Q for the upper. The 34s uses both symbols exactly vice versa. Thar's why I think either the symbol should be changed or the values should get the opposite sign:
x = 1,5 => Q = 0,06681
x = -1,5 => Q = 0,93319
Q = 0,1 => x = 1,28155
Q = 0,9 => x = -1,28155
- Regarding Sigma-plus: I never understood why this function should require a primary key. Even in the days when I used statistics virtually every day I never used this function on any of my calculators. I always wondered if someone really used this function at all. ;-) Using my 41C it always drove me mad when I wanted to start a program at label A, but instead Sigma+ was executed because I forgot to turn on user mode. And so one accidental key press destroyed not less than six memory registers. No, LastX Sigma- is not always an option.
In other words: If I could design a calculator, this Sigma+ key would be the first function I'd remove from a primary key. The 34C uses f Sigma+ and g Sigma-, which is perfectly okay. In simple words: yes, I want a decicated "A"-key.
Otherwise I think an actual "hardware" 34s would be one of the greatest calculators I ever used. ;-)
Edited: 24 Mar 2011, 6:36 p.m. after one or more responses were posted