Backed into corner on HP48GX



#2

I was learning the equation solver, hit solver and entered an equation but it didn't work out, I wanted to delete that equation and start another one but can't get to the edit mode. I have a bunch of stack objects, like list 1 and #'s, but can't clear them out or anything. Nothing I do seems to be able to clear the stack or get back to delete the original equation. Not sure what to do here. Tried a bunch of buttons, drop, next, back, clear, purge, nothing I do helps. HELP! For some reason the top bar says pgm and I don't know how I did that, I didn't start out in program mode.


#3

Have you tried "ON" or "ON+C" ?


#4

Quote:
Have you tried "ON" or "ON+C" ?

Yep, tried that of course, not sure what to do.


#5

If ON+C does not fix things I don't have any real good ideas that don't result in a Memory Lost state. Anything else I can think of would potentially lose your RAM. I am guessing that you don't want to pull the batteries because you don't have a current backup? You say that "PGM" is displayed on the status line? That indicates that you are in program entry mode. Are you using the built-in editor or a third part tool? Not that the answer to that really helps, just wondering.


#6

I was just using the built in 'solver' function, where you get the line to input an equation and such. I imagine an expert could get me out of trouble in seconds if he actually had it his hands but it sure is flummoxing me!


#7

I don't know why it worked now, but doing 'solve' again got me back to the beginning, was able to delete the formula. Now I can start over! The formula btw, is one used to calculate chess ratings, I was starting with the 'win expectancy' part of it:

1/(10^((opponents rating-your rating)/400)+1)
One question I have is, on a casio scientific calculator, you have the ^ function isolated so you can do 10^ or 4^ or whatever but I don't see just the ^ function on the HP. Is it there somewhere? It has a 10^x function but it calls itself 'ALOG()'. Is that exactly the same thing as 10^ ? I put that expression in using variables O for opponents rating and Y for Your Rating to see if it would solve ok, and assigned 1500 to each variable (the results in that case better be 0.5, the expected win percentage of two chess players with the same rating (1500 in this case). I was not able to get expression solve to work, it just sat there. Doing it again, I input
1/(ALOG((O-Y)/400)+1) and it gives an Invalid Syntax error message.
with ALOG highlighted. What am I doing wrong? Thanks for your help eveyone!

Edited: 1 Sept 2010, 1:43 p.m.


#8

Quote:
I don't know why it worked now, but doing 'solve' again got me back to the beginning, was able to delete the formula. Now I can start over! The formula btw, is one used to calculate chess ratings, I was starting with the 'win expectancy' part of it:

1/(10^((opponents rating-your rating)/400)+1)
One question I have is, on a casio scientific calculator, you have the ^ function isolated so you can do 10^ or 4^ or whatever but I don't see just the ^ function on the HP. Is it there somewhere? It has a 10^x function but it calls itself 'ALOG()'. Is that exactly the same thing as 10^ ? I put that expression in using variables O for opponents rating and Y for Your Rating to see if it would solve ok, and assigned 1500 to each variable (the results in that case better be 0.5, the expected win percentage of two chess players with the same rating (1500 in this case). I was not able to get expression solve to work, it just sat there. Doing it again, I input
1/(ALOG((O-Y)/400)+1) and it gives an Invalid Syntax error message.
with ALOG highlighted. What am I doing wrong? Thanks for your help eveyone!


I got past that by re-entering the formula and have the formula highlighted and hit EXPR= it came up with a solution but put a number of 201166.1581 in the "O" variable slot which previously held 1500. Any reason why? I thought, stupid me, that with the formula highlighted and you hit EXPR= it should come up with 0.5, the correct answer but I didn't want it to 'solve' for O. I wanted to just input O and Y and solve the frigging expression but no joy yet. ??
It also took a minute or two just to calculate that rediculous 201166 number. Why would it take so long for this simple expression?

My impression is that ALOG is not the same as 10^ on the casio. I did the same thing, but with the O=1500 highlighted and after that long delay it came up with the same number. Any ideas here? Thanks for your patience with my bumbling here.


Edited: 1 Sept 2010, 3:37 p.m.


#9

If you solve 'P=1/(10^((O-Y)/400)+1)' for R, assuming you have assigned 1500 for O and Y, you will get P=0.5. Is this what you are looking for? By the way, exponentiation is accessed through the y^x key, but if you prefer you can use the ALOG function instead of 10^x, of course.

Edited: 1 Sept 2010, 4:04 p.m.


#10

Beat me to it <g>.


#11

Just found the formula and some theory:

http://www.chessrankings.com/theory.aspx

I am a patzer at chess, now I'll be able to measure my patzerness :-)


#12

Do you play chess online? The site I play at is called Red Hot Pawn, redhotpawn.com where you can take 3 days to make a move if you want, you can play for free as long as you play a max of 6 games at once or about 30 bucks a year for full subscription. The thing I like there is the forum system. There are separate forums for sports, religion, debates, science, general topics, puzzles and posers, and the like. My handle there is Sonhouse, I play blues on guitar and Son House was one of the great ones. You can access anyone's games and play them over, you can record your own games and play them back if you want to improve your own skills. I think it's a great site. There are others of course but a lot of other sites like Pogo games and Yahoo have some real asssholes who boost their ratings using computer programs like Fritz or Rybka to play the games and you don't have a chance against those extremely strong programs but at RHP they have people who check out games of suspicious nature, they can match the game play against a certain CPU/program combination and find an almost total match between the players moves and the moves generated by some combination cpu/pgm and when they spot that they kick that person off the site. There have been many people kicked off that way so it leaves the rest with a fair degree of confidence you are playing an actual person not some chess engine. So that's my story and I am sticking with it:)
Check the place out, it's a blast. I contribute to the puzzles forum, the science forum, the culture forum a lot as sonhouse.


#13

No, I don't play chess online. I tried it a couple of times, it's really better than playing against the computer, but I think I have to improve my game a bit before getting back. Some years ago I played blitz 5-minutes games at work during lunch-time on a regular basis. I have Ubisoft's ChessMaster (Grandmaster edition), but I don't play with it often. Also I have Leonard Barden's "Play Better Chess", but haven't read it seriously yet. Thanks for the tip, anyway.


#14

RHP has over 100,000 members, and at all levels. Try it out, it's free, there are people with ratings from 700 to 2400 there. You can find your level and work up from there for sure. Anyway, good luck.

#15

Quote:
If you solve 'P=1/(10^((O-Y)/400)+1)' for R, assuming you have assigned 1500 for O and Y, you will get P=0.5. Is this what you are looking for? By the way, exponentiation is accessed through the y^x key, but if you prefer you can use the ALOG function instead of 10^x, of course.


Yes, if you use most any equal rating you will get 0.5 as the answer, 1200 V 1200, 2400 V 2400, etc. That just means if you are both say, 1600, and you play 100 games, you are pretty sure of winning 50 games and losing 50 games or drawing all games, like most of the games of the Kasparov/Karpov matches, titanic struggles that ended up one game up after something like 130 games, not in one match of course, but they tied a lot of games!

So to use Y^x you would go say, 10, enter, Y^x, ((bla bla bla)) for the exponent? or in the equation solver, 10, Y^x, ((Bla))? Does it recognize that last as the proper format for exponents?

I was just sneaking up on the full rating formula, it's a bit more complex than just the win expectancy part, but I wanted to get that right before I finished the rest. The win expectancy is the key, if you don't have that right you are screwed trying to get the change in rating after a game.

Well it sure isn't working like I thought it should, I simplified the expression just to see it work, I entered 4/6 in the equation line of the 'solve' function and hit EXPR= and the exact same thing happened, the hourglass came on for about a half second, goes off and nothing else happens, no answer pops up. What am I doing wrong here?

Ok, figured that one out. You have to hit NXT and do CALC and EVAL, THEN the frigging answer comes out.


Edited: 1 Sept 2010, 10:37 p.m. after one or more responses were posted


#16

Don,

I entered it on a 48SX (GX should be identical--if you have issues I'll dig my GX out) exactly as you presented it and it worked perfectly. Here are the Keystrokes I used (more or less)

'P=1/(10 Y^X ((O-Y)/400)+1)'

ENTER

'RATE'

STO

LftShft-SOLVE

'RATE'

STEQ (soft menu)

SOLVR

1500 O

1500 Y

LftShft-P


Fraction of a second later I get 0.5

Hope this helps.

Edited: 1 Sept 2010, 10:27 p.m.

#17

Don,

I tired it on the 48GX and it is slightly different. Here are the keystrokes after entering the equation:

LftShft-SOLVE

ROOT (sub menu)

'RATE'

LftShft-EQ (stores the equation)

SOLVR (and then you are at the soft menu where you enter your
variables)

1500 O

1500 Y

LftShft-P

Note that on the GX you can also do this with a CHOOSE menu.

RgtShft-SOLVE (pulls up a window menu)

Solve equation (first option-already selected)

OK

CHOOSE (soft menu to select your equation)

'RATE' OK

use the arrow keys, the number keypad, and OK to enter your knowns.

Use the arrow keys to go to your unknown (P) and hit SOLVE (soft menu)


#18

Thanks, I was having a bit of trouble with the SX version, that's a big help.

I was considering this a training exercise to do the whole rating formula as a real program rather than just an equation solver thing. I guess it wouldn't make a lot of difference but I want to do the program thing also, it adds score, K factor and so forth.


Edited: 1 Sept 2010, 11:35 p.m.


#19

No problem. I'm happy to help when and where I can. Sometimes I have to do my real work which is a whole lot less fun but I should not complain-playing around with computers all day is not the worst thing in the world.

Cheers


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