Understanding the HP 28S XPON function
02-25-2017, 12:21 AM
Post: #1
 mbrethen Junior Member Posts: 40 Joined: Dec 2013
Understanding the HP 28S XPON function
I guess I don't quite understand the usefulness of the XPON function on the HP 28S for symbolic expressions. I tried to evaluate the expression XPON("X^3") using ->NUM but it returns the error: Undefined Name. How does one, for example, determine the degree of a polynomial expression?
02-25-2017, 06:40 AM
Post: #2
 Joe Horn Senior Member Posts: 1,967 Joined: Dec 2013
RE: Understanding the HP 28S XPON function
XPON is only for real numbers, not algebraic objects. HP 28S RPL does not contain a command that returns the degree of a polynomial. The DEGREE command which does that was introduced into RPL later, in the HP 48G.

<0|ɸ|0>
-Joe-
02-25-2017, 12:43 PM
Post: #3
 Werner Senior Member Posts: 798 Joined: Dec 2013
RE: Understanding the HP 28S XPON function
Probably the 50G, Joe. The 49G AUG does not know DEGREE.
(I have only a 48 and a 49, and I never heard of it - but that's not a reliable reference ;-)

Cheers, Werner

41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE
02-25-2017, 03:40 PM (This post was last modified: 02-25-2017 04:00 PM by mbrethen.)
Post: #4
 mbrethen Junior Member Posts: 40 Joined: Dec 2013
RE: Understanding the HP 28S XPON function
I wonder if this can be successfully programmed for the 28s? One thought I had is to perform successive differentiation until you end up with a constant? A loop counter could keep track of the number.

Another idea is to evaluate the polynomial using Horner's method (PVAL in the Math Applications reference) and then SIZE the nested list.
02-25-2017, 04:40 PM
Post: #5
 Joe Horn Senior Member Posts: 1,967 Joined: Dec 2013
RE: Understanding the HP 28S XPON function
(02-25-2017 12:43 PM)Werner Wrote:  Probably the 50G, Joe. The 49G AUG does not know DEGREE.
(I have only a 48 and a 49, and I never heard of it - but that's not a reliable reference ;-)

The 49G with firmware version 1.19-6 contains a DEGREE function that returns the degree of a polynomial. It's listed in the 49G's built-in CATALOG, and it has a help screen.

The 49G AUG is unfortunately missing an astounding number of 49G commands (at least they are missing from its Command Index on pages 427-432), including the following:
• ALGB
• ASSUME
• AUGMENT
• BASIS
• C2P
• CASCMD
• CHOLESKY
• CIRC
• COLLECT
• CONSTANTS
• CYCLOTOMIC
• DEF
• DEGREE
• DIAGMAP
• DISPXY
• DISTRIB
• DOMAIN
• DROITE
• EXP&LN
• EXP2HYP
• EXP2POW
• EXPLN
• FDISTRIB
• GAMMA
• GBASIS
• GRAMSCHMIDT
• GREDUCE
• HELP
• HYPERBOLIC
• IBASIS
• IMAGE
• INTEGER
• ISOM
• KER
• LASTARG
• LOCAL
• MAIN
• MATHS
• MKISOM
• MODULAR
• MSLV
• OLDPRT
• P2C
• PLOT
• PMINI
• POLYNOMIAL
• POP
• POTENTIAL
• POWEXPAND
• PUSH
• RCLVX
• REWRITE
• RULES
• SERIAL
• SIMPLIFY
• SREV
• STORE
• STOVX
• STURM
• STURMAB
• SYST2MAT
• TAN2CS2
• TESTS
• UNASSIGN
• UNASSUME
• UNBIND
• VPOTENTIAL
--- the commands in Library 256 are not included in the list above, but they were not in the 49G AUG either.

<0|ɸ|0>
-Joe-
02-25-2017, 09:25 PM
Post: #6
 Werner Senior Member Posts: 798 Joined: Dec 2013
RE: Understanding the HP 28S XPON function
I stand corrected ;-)
At least it's the 49, not the 48 ;-)

Werner

41CV†,42S,48GX,49G,DM42,DM41X,17BII,15CE
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