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I am curious, which program or programs do you get the most value out of having on your handheld: games, extended functionality? Be specific please.
As for myself, I write small routines that apply to my work. I am in the eyeglass manufacturing industry, so I write routines for cylinder transposition, radius to diopter conversions, etc. None of these are very sophisticated, but just make things easier.
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I do research in and teach chemistry and physics; I got tired of converting from eV to nm or Å, and so I just wrote a short routine to do this for me. Also, HP calculator constant libraries generally list R, the gas constant in the proper, SI term of joules; and since I often need the ancient, but still oftused latm, there's a little program for that. And then, there's a suite of four that I use often for calculating average, median, mode, maximum, and minimum of a set of data. The mode program is, I guess in today's terminology, still under construction; maybe I'll try to fix it one of these nights now that baseball season is over (although it's been several baseball seasons now!)
Other ones:
one to calculate the Miller Indices (in the Museum program archives!) of planes in cubic crystals from their 2theta reflections (not for me myself, but I use it generally to make sure students don't pull a fast one). This one took a while to complete (and cubic is EASY); I'm not sure I want to contemplate routines for less symmetric unit cells.
one
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Quote:
As for myself, I write small routines that apply to my work.
Ditto, civil/structural engineering. And business functions, too.
Quote:
None of these are very sophisticated, but just make things easier.
That's exactly what handheld calculators are for, these days. The heavy number crunching is best done on the computer.
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Some specific examples:
Very simple formulas like the Rational one for calculating peak discharge from a small watershed.
Or the ACI formula for determining minimum steel in a concrete beam.
Or a formula for determining screw anchor capacity for a bulkhead.
Sometimes a more complicted one that uses nested IF's on the 27s, to follow Florida rule for calculating onsite waste flow based on floor area.
Like others have said, I often write quick short ad hoc routines that are later discarded.
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Lately the ones that get used the most are mW to dBm and back and THz to nm and back  very simple but speeds up debugging when I can just push 1 or 2 buttons.
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Date/time calculations. I use my own date program on HP35s which gives date, dayofweek, moonphase (for fun) and makes time<>unixtime conversions.
Curve fitting, by stefanv http://www.stefanv.com/calculators/hp35s_curve_fitting.html
I also have IP netmask calculator, but my brain computes faster (20 years in IP networking).
I'd like to see more reallife applications, especially numerical.
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I do not have a technical job, but I am an avid runner. In the past, I created routines (mostly on my 11C, later on a few RPL calcs) to calculate speed/distance information, lap times, race time prediction on different distances, and (drum roll) a routine that combines distance, speed and heart rate into an overall indication of fitness.
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I don't know which one I use the *most*, but I can give an example of something I did with programming not too long ago.
I was trying to calculate the transmission of light through a film as a function of wavelength given the film's index of refraction. The formula for it, in the appendix of this paper, is incredibly complicated. I was using Excel and getting wrong answers.
So I went back to first principles and calculated the formulas myself on my HP50g. This is easy, much easier than entering the formulas in Excel. The starting point for the formulas are not so complicated if you allow n to be complex, which the HP50g can do, and the HP50g can do the algebra of the derivations (it involves working with symbolic matrices, another forte of the HP50g). So not only is it easy, it's almost impossible to make a mistake. Then I loaded in n as a function of wavelength through the SD card in a CSV file, calculated the transmission, wrote that as a CSV file on the SD card, and loaded it back into Excel. Then I went through my Excel file until I found my transcription errors and the Excel result matched my calculator result.
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...wrote that as a CSV file on the SD card...
How did you do that? Did you use the SDLib library (L935],
http://www.hpcalc.org/details.php?id=6524
or is there another way?
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Mostly, I write quick and dirty programs to automate mundane calculations. They get written, used and thrown away.
I don't remember any specific ones unfortunately.
 Pauli
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Or you just write the code for entirely new calculators in your spare time :)
I just flashed my own, btw, thank you for your effort in that!
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Quote: Or you just write the code for entirely new calculators in your spare time :)
It is the only way to get the functions I want in a device ;)
 Pauli
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I am an Electrical Engineer in the telecommunications industry. I have written many, many small programs, primarily to automate conversions of data. Examples include Dbm to various audio levels, DB to gain, frequency response, clock and logic calculations, etc.
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I have been using the multiple equation solver on the 50g quite a bit.
I have a few different sets of equations in directories.
 Hydraulic Pump Calculations
 Hydraulic Cylinder Calculations
 Short Motion Profile Calculations
It really helps me to be able to type in known values and solve for unknowns. I never know ahead of time which values will be the knowns / unknowns and it usually changes several times when iterating through a problem.
Other than that, I use the bases when working with industrial controllers.
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I use my calculators for mathematics. My favorites would have to be: the quadratic equation, zeta function, matrix operations, and functions used for summation. I am not a gamer (any more).
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You're a likely candidate for the 34S. :)
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I also mostly use my calcs for short routines to help me figure out the stuff I'm working on. I'm currently a Comp. Sci. PhD candidate, working on computational trust, and most recently I've been working on the use of utility functions to model risk aversion in intelligent agents. A few keystrokes on the 41CX and I can have a routine which will let me play with the numbers and figure out which of various candidate functions seems most appropriate.
The 48GX was handy for plotting the functions, at least for the simple cases. However, when it comes to more complex 3D plots, I found it easier to whip up some Java code using the jzy3d library (especially since I'm doing a lot of simulation work in Java anyway).
I've also made heavy use of the 41CX for basic statistical number crunching, particularly calculating mean values across multiple simulations in my early experiments. Hopefully the 15CLE will be able to take over some of that load. . .
Best,
 Les
[http://www.lesbell.com.au]
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Most of my programs are extended functionality or frequently made calculations. For reference, I work in the field of statistics and data analysis.
Probably my most frequently used program is something that calculates the standard deviation of a binomial distribution using the normal (Gaussian) approximation.
For a long while I was doing a specific datemath calculation and whipped up a program on my 15c to handle it for me. I was using that all the time for benchmarking an analysis routine I was running, but as that project has since moved on, so has the program.
Edited: 3 Oct 2011, 5:30 p.m.
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Right now it'd be computing the number of pixels in a circle.
I used to use the MES on my 50g and 42S, but not so much anymore.
