General > General Technical Chat

What calculator do you use ?

<< < (20/84) > >>

ejeffrey:
I mostly use google calculator or matlab.  Google calculator for its ability to do arithmetic on dimensioned quantities, and it is sufficient for 99% of cases where I would use anything resembling a hand-held calculator.  I use matlab for plotting, or for doing more complicated math/programming.

I do have a calculator on my phone which I use as a last resort.

For hand held calculators I used to love my HP48GX, but I haven't used it in ages.

saturation:
As another posted said, the scientific calculator is dying, if not already dead, IMHO.  Its primary use in my observation, is education.  VPAM, graphing etc., are mostly for novice users, which is currently the target market for calculators.

The key issue is after you make a calculation, what do you do with the result?  Integrate it into another program for further processing?  Enter the result in field, in a computer?  So, for the most part, calculators today for professional use are mostly for back of envelope brainstorms, and quick approximations, rather than for precision work.

Even in the simplest use, debt or mortgage calculations, actual results by banks use very high precision numbers, 2-30x more than a general scientific calculator.  However when sitting down with the bank agent, they are opt to use a calculator to give the customer a ballpark figure.   Often a feature of a  specific 'financial calculator' is they do have higher precision numbers compared to a general scientific or programmable one [ 16-32 bit numbers in financial, versus 10 or 11 digits in the Casio FX260] or present the amortization table on a PC their working with, again making the calculator superfluous.

So, in the end, the modern scientific calculator is more like the slide rule was before 1980, to make estimates, but instead of breaking out the log or trig tables and extending the precision, we punt it to computers instead.

RealCalc puts a scientific calculator on my Android phone, and I use it about as much as my FX260, but the cramped screen makes it less attractive to reach for.  Its main appeal is it works very much like the FX260.

george graves:
TI-89 Titanium.  I wish I had gone for just the regular ti-83 looking back.

slateraptor:

--- Quote from: saturation on April 23, 2012, 12:21:50 pm ---So, in the end, the modern scientific calculator is more like the slide rule was before 1980, to make estimates...

--- End quote ---

I hope you'll excuse me for raising an eyebrow when a NIST engineer speaks of numerical "estimates". :P

ejeffrey:

--- Quote from: saturation on April 23, 2012, 12:21:50 pm ---Even in the simplest use, debt or mortgage calculations, actual results by banks use very high precision numbers, 2-30x more than a general scientific calculator.

--- End quote ---

This is actually a myth propagated by financial types who don't understand math.  Financial transactions are rounded to the nearest penny, and intermediate values in a financial calculation will be rounded aggressively at every step along the way.  A double precision float has an effective 53 bit significand, more than enough dynamic range for financial calculations on any scale smaller than the GDP of a G8 country.

The problem is simply that (binary) floating point arithmetic of any precision is unsuitable for financial transactions because certain values are not representable.  You can't represent $0.10 exactly in as floating point number.  When written in base 2, the number 1/10 is an infinitely repeating fraction, so it can't be captured exactly with any finite width number.

The upshot of this is that if I transfer $0.10 to your bank account, and our balances are represented as floating point numbers, the total amount of money before and after the transaction is not constant.  This is obviously bad!

So financial calculations must be done either with integers (representing cents), or decimal (BCD) representations.  It isn't that the financial type necessarily has more resolution, it simply has the specific type of rounding behaviour required for financial transactions.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod