Amortize specific period ranges

[Dave Britten]

I just refinanced our house, and in the process, discovered a financial feature I really like: being able to amortize a specific, arbitrary (but contiguous) range of periods.

For example, we've made 73 payments on the old loan. I can just punch in 1 to 73 (the actual input method differs by calculator), and amort those payments, giving me total interest and principal paid so far, as well as remaining balance. Pretty much every financial can do that part.

But if I want to amort the remaining portion of the loan, not all calculators will let you enter 74 - 360, and amort those. Often you have to amort the first 73 payments, subtract 73 from the total number of payments, then amort that many remaining payments. Not a HUGE deal, but extra steps that are a bit annoying when doing a bunch of what-ifs and playing with numbers.

These are the models I found that let you punch in any range of payments and amort those, optionally advancing to the next set of an equal number of periods. What else can do it? I'm interested in any of the inferior non-HP brands too.

10B
10BII
10BII+
TI BAII Plus (I really like the feature set, but the keyboard misses keystrokes with fast typing, and it's really light and has no rubber feet. You have to chase the damn thing all over your desk.)
TI BAII Plus Professional
Sharp EL-533 (Pretty slow amorts on this one, but it's so delightfully petite.)

Also, I'm sure I could program it on the 41C easily enough, but considering it's pretty slow at amorts, I could compute this kind of stuff manually much faster on, say, a 10BII+.

A further annoyance on the 12C and 14B is that they also update the values stored in n and PV to represent the total periods amortized so far and the remaining balance respectively.

Can this be implemented easily with a 17BII solver equation? I don't see any amort functions mentioned in the manual, and I don't think you can directly reference the values stored in the TVM variables.

[Dave Britten]

...And just for fun/reference, here are the approximate amort times for 360 periods on a few different models.

n=360
i%/yr = 4.75
PV = 138,446.00
PMT = -722.20 (unrounded value, obtained via TVM solver)

10B: 4.25s
10BII: 3.5s
10BII+: 0.25s
12C (original, not ARM version): 1m27s
14B: 7.25s
17BII: 4.25s
200LX: 4s
Sharp EL-533: 46s
TI BAII Plus: 2.75s

[rprosperi]

(06-20-2015 01:31 AM)Dave Britten Wrote:  ...And just for fun/reference, here are the approximate amort times for 360 periods on a few different models.

n=360
i%/yr = 4.75
PV = 138,446.00
PMT = -722.20 (unrounded value, obtained via TVM solver)

10B: 4.25s
10BII: 3.5s
10BII+: 0.25s
12C (original, not ARM version): 1m27s
14B: 7.25s
17BII: 4.25s
200LX: 4s
Sharp EL-533: 46s
TI BAII Plus: 2.75s

Interesting results, I had no idea the 10BII+ is so much faster than the 10BII. Then again, I don't recall ever doing anything that wasn't effectively instant on these machines. Thanks for the testing and sharing results Dave.

[Don Shepherd]

(06-20-2015 01:02 AM)Dave Britten Wrote:  Can this be implemented easily with a 17BII solver equation? I don't see any amort functions mentioned in the manual, and I don't think you can directly reference the values stored in the TVM variables.

Dave, could the solver functions USFV() or USPV() give you what you want? I remember using them years ago for a project, but I can't remember the details now. I do remember thinking at the time, however, that they are very useful in certain situations.

I think you are right about not being able to reference the TVM variables in a solver equation, but I seem to recall that the 19bii solver (unlike the 17bii solver) did have some functions for those values.

Don

[Dave Britten]

(06-20-2015 01:45 AM)Don Shepherd Wrote:  

(06-20-2015 01:02 AM)Dave Britten Wrote:  Can this be implemented easily with a 17BII solver equation? I don't see any amort functions mentioned in the manual, and I don't think you can directly reference the values stored in the TVM variables.

Dave, could the solver functions USFV() or USPV() give you what you want? I remember using them years ago for a project, but I can't remember the details now. I do remember thinking at the time, however, that they are very useful in certain situations.

I think you are right about not being able to reference the TVM variables in a solver equation, but I seem to recall that the 19bii solver (unlike the 17bii solver) did have some functions for those values.

Don

I believe you can use USPV and USFV to do TVM calculations "by hand" if necessary (though the 19BII has actual TVM functions in the solver). I don't see any functions for directly performing amortization, so you would probably have to do it yourself with the usual sum function.

[Katie Wasserman]

(06-20-2015 01:41 AM)rprosperi Wrote:  Interesting results, I had no idea the 10BII+ is so much faster than the 10BII. Then again, I don't recall ever doing anything that wasn't effectively instant on these machines. Thanks for the testing and sharing results Dave.

The 10bii+ is not only fast it has a really nice set of functions. It's got the same ARM processor as the 12C+, 15C+, 20b, 30b, etc.. If it had an RPN option it would definitely be my favorite non-programmable calculator.

[Katie Wasserman]

(06-20-2015 01:31 AM)Dave Britten Wrote:  ...And just for fun/reference, here are the approximate amort times for 360 periods on a few different models.


12C (original, not ARM version): 1m27s

The latest version 12C+ does this in about 0.9 seconds, as close as i can measure it.

[Katie Wasserman]

(06-20-2015 01:02 AM)Dave Britten Wrote:  These are the models I found that let you punch in any range of payments and amort those, optionally advancing to the next set of an equal number of periods. What else can do it? I'm interested in any of the inferior non-HP brands too.

You can certainly do this on the HP 20b/30b.
The Casio fx-9860 series does this really nicely too.

[Marcus von Cube]

I just played around with my 10bII+ und stumbled across a funny thing: The display format is not correctly honored by the BAL display. The Value shows one excess digit. With DISP 2 the display shows 0.040 instead of 0.04. Bug or feature?

[Dave Britten]

(06-20-2015 03:40 AM)Katie Wasserman Wrote:  

(06-20-2015 01:02 AM)Dave Britten Wrote:  These are the models I found that let you punch in any range of payments and amort those, optionally advancing to the next set of an equal number of periods. What else can do it? I'm interested in any of the inferior non-HP brands too.

You can certainly do this on the HP 20b/30b.
The Casio fx-9860 series does this really nicely too.

I would have tried it with my 30b, but it's currently a 34s.

[Katie Wasserman]

(06-20-2015 08:15 AM)Marcus von Cube Wrote:  I just played around with my 10bII+ und stumbled across a funny thing: The display format is not correctly honored by the BAL display. The Value shows one excess digit. With DISP 2 the display shows 0.040 instead of 0.04. Bug or feature?

I vaguely remember that this was a bug in early versions. It works ok for me in version 12-10-2012 and later versions. What firmware do you have in yours?

[Marcus von Cube]

(06-20-2015 02:54 PM)Katie Wasserman Wrote:  I vaguely remember that this was a bug in early versions. It works ok for me in version 12-10-2012 and later versions. What firmware do you have in yours?

It's definitely older (from 2010). Can you point me to a download?

[Dave Britten]

(06-20-2015 02:54 PM)Katie Wasserman Wrote:  

(06-20-2015 08:15 AM)Marcus von Cube Wrote:  I just played around with my 10bII+ und stumbled across a funny thing: The display format is not correctly honored by the BAL display. The Value shows one excess digit. With DISP 2 the display shows 0.040 instead of 0.04. Bug or feature?

I vaguely remember that this was a bug in early versions. It works ok for me in version 12-10-2012 and later versions. What firmware do you have in yours?

Mine's "7-13-2010 2", but doesn't appear to have the bug. I'd be interested in updating if there's a firmware image and instructions floating around (presumably just a quick MySAMBA flash job).

[Katie Wasserman]

(06-20-2015 04:57 PM)Marcus von Cube Wrote:  

(06-20-2015 02:54 PM)Katie Wasserman Wrote:  I vaguely remember that this was a bug in early versions. It works ok for me in version 12-10-2012 and later versions. What firmware do you have in yours?

It's definitely older (from 2010). Can you point me to a download?

Check your email.

[rprosperi]

(06-20-2015 03:29 AM)Katie Wasserman Wrote:  

(06-20-2015 01:41 AM)rprosperi Wrote:  Interesting results, I had no idea the 10BII+ is so much faster than the 10BII. Then again, I don't recall ever doing anything that wasn't effectively instant on these machines. Thanks for the testing and sharing results Dave.

The 10bii+ is not only fast it has a really nice set of functions. It's got the same ARM processor as the 12C+, 15C+, 20b, 30b, etc.. If it had an RPN option it would definitely be my favorite non-programmable calculator.

Indeed, the 10BII+ is likely the best calculator for the dollar out there. Tim packed a ton of stuff in this nice machine, which is sadly ignored by most folks due to it being Algebraic and Financial and Entry-Level, a lethal combination for most HP users. Surely it's the best Entry-Level Calculator I recall using...

[BruceH]

(06-20-2015 01:02 AM)Dave Britten Wrote:  I'm interested in any of the inferior non-HP brands too.

10B
10BII
10BII+
TI BAII Plus (I really like the feature set, but the keyboard misses keystrokes with fast typing, and it's really light and has no rubber feet. You have to chase the damn thing all over your desk.)
TI BAII Plus Professional
Sharp EL-533 (Pretty slow amorts on this one, but it's so delightfully petite.)

I'm pretty sure the BWK Business Professional[1] can do it but mine is tucked away in a box somewhere and I can't lay my hands on it at the moment.

(06-20-2015 01:02 AM)Dave Britten Wrote:  Also, I'm sure I could program it on the 41C easily enough, but considering it's pretty slow at amorts, I could compute this kind of stuff manually much faster on, say, a 10BII+.

Well, if you're going to allow programmables then the 48,49,50 series all have TVM functions so you could easily program it on those.

[1] Sadly, it looks as though they have gone out of business - I couldn't find the manufacturer's web site via a quick Google.

[Gene]

(06-20-2015 03:29 AM)Katie Wasserman Wrote:  The 10bii+ is not only fast it has a really nice set of functions. It's got the same ARM processor as the 12C+, 15C+, 20b, 30b, etc.. If it had an RPN option it would definitely be my favorite non-programmable calculator.

Gene: Agreed, it is by FAR one of my favorite machines. RPN is the only missing feature, but I am very glad it has hierarchy at least for an AOS type feel.

HP did good with this one!

[Dave Britten]

(06-24-2015 08:45 PM)Gene Wrote:  

(06-20-2015 03:29 AM)Katie Wasserman Wrote:  The 10bii+ is not only fast it has a really nice set of functions. It's got the same ARM processor as the 12C+, 15C+, 20b, 30b, etc.. If it had an RPN option it would definitely be my favorite non-programmable calculator.

Gene: Agreed, it is by FAR one of my favorite machines. RPN is the only missing feature, but I am very glad it has hierarchy at least for an AOS type feel.

HP did good with this one!

It's got a higher rating on Amazon than the TI BAII Plus (though with a smaller population size, and I don't know about the standard deviations). I tend to agree with that; the TI has a very nice feature set, and the worksheet paradigm is easy to use, but it has no rubber feet, and misses keystrokes like crazy with no two-key rollover.

[Dave Britten]

I just got a Sharp EL-738. It does arbitrary-range amortization like the others, and it's reasonably quick, doing 360 periods in about 2 seconds.

Overall, I really like it. The keyboard is excellent. The keys are nice and soft, but with just enough tactile feedback and noise, and the numeric and operator keys are nice and large (11 mm by 8 mm, with 3.5 mm spacing). The two-key rollover is great, and you can type extremely quickly. I haven't seen it miss a keystroke yet.

It's also got scientific functions (trig, logs, exponents, hyperbolics, and basic probability and combinatorics), plus statistics with 6 different regression models and up to 50 data pairs. No degrees/hours-minutes-seconds conversion, unfortunately, but it does compute days between dates, dates n days from a given date, and days of the week.

Usage is very much like the TI BA II Plus, with the whole worksheet setup, which is nice if you need to quickly get up to speed with a function you've never used, or which you use infrequently. You can easily edit, insert, and delete both cash flow and statistical data after it's been entered. The manual is pretty good, and has several examples.

My main gripe is that read-only worksheet values can't be directly used in calculations. So if I amortize a payment range, and want to accumulate the interest values in a storage register, I can't calculate with that output directly. There's a workaround: when you display a value in a given worksheet, it's automatically stored in ANS. Just press ON/C to exit the worksheet, and you can then use ANS to work with the last displayed value. The downside is that this involves a few extra keystrokes, and the values for P1 and P2 will reset to 1 when you go back into the amort worksheet. Not a deal-breaker, though, and not nearly as big a flaw as I've found in other models (like that awful TI keyboard). I'd rather have a few extra steps for this occasionally used function than missed keystrokes everywhere. And if I'm doing that for more than just a couple groups of payments, I'm probably doing it with 1-2-3 on my 200LX anyway.

I might have to check out some of the Sharp scientifics and see how they compare.