Thread: Higher Mathmatics !!! about the Razor angle...

Is Gugi/are you (perspective is a bitch) using matlab to do the razor angle compilation?



Note: This is a split from the data collection thread on razor angle here : http://straightrazorpalace.com/razor...zor-angle.html

Thanks
gssixgun

Originally Posted by khaos

Is Gugi/are you (perspective is a bitch) using matlab?

Matlab is great for lots of things, but to keep track of all the individual data, My money is on an Excel (or similar) spreadsheet. People don't give Excel enough credit for analyzing data. It has powerful enough math features to handle this kind of thing with ease.


Here is a post from the "my bevel angle calculations" thread. This formula gives an accurate representation of the bevel angle with multiple layers of tape, one layer of tape, or no tape at all.

x = spine width
y = distance from spine/hone contact point to tip of bevel with no tape on spine
n = number of tape layers
t = thickness of tape
Θ = total bevel angle °


total bevel angle:

Θ = 2{arctan[(.5x + nt)/{ycos(arcsin{.5x/y})}]}

arcsin(.5x/y) gets you the angle on one side of the bevel, then y times cosine of the resultant angle gets you the width of the razor that I was formerly calling w.

This allows for w to remain constant no matter how many layers of tape are added, eliminating the need to 1.) remeasure the hypotenuse every time you add a layer of tape, and 2.) measure w (acutal razor width) initially, which could be difficult to do accurately.

Well, if one were to create a couple of vectors in matlab, its simple enough to add in a loop to extend them when adding data points. It can then make a chart out of them just like excel can. The difference being in matlab you can personalise it a lot more. Excel everything has to be set up just right...

Also noticed you are taking a cos of an arcsin? why? sin=a/c so cos would be sqrt(c^2-a^2)/c... in this situation cos()= y^2-.25x^2/y, and ycos() would then be... y^2-.25x^2 which is a lot simpler than that whole job there...

Gugi is a computer. He does the calculations in his head.

Damn, my grandson has hidden my abacus and slide rule.

Originally Posted by Slartibartfast

Gugi is a computer. He does the calculations in his head.

I'm math challenged. I find an on-line calculator for determining the angle. Or do it the old fashioned way - plot it out on paper and use a protractor.

Why would you even consider proprietary software when you can use R? R is free, does vectorised calculations without the need for time-intensive looping (if you are clever enough), and creates fully customisable publication-quality graphics (allowing latex-like syntax for symbolic axis labels and plot titles). It even allows output to be directly exported into latex via Sweave.

Furthermore, given that by default the data collected in the present case is by necessity a sample from the population of all straight razors, if the need arises in the future to infer relationships or parameters from the general population, R allows stochastic non-linear modelling using state-of-the-art optimisation algorithms (ranging from the tried and true Quasi-Newton - based procedures, newton-raphson, through to genetic algorithms, simulated annealing etc) . If that proves insufficient (which is highly unlikely in the present case), R allows you to write your own code in Fortran, C, or C++, and interface that back into the integrated environment via pointer referencing (in the case of the C-like languages). It is also, in and of itself, an object-oriented programming language with a C-like structure, so you may take advantage of the plethora of pre-written code upon which the many inbuilt R functions are based.

Matlab, Excel........ Don't make me laugh!!!

James.

Originally Posted by Ben325e

This allows for w to remain constant no matter how many layers of tape are added, eliminating the need to 1.) remeasure the hypotenuse every time you add a layer of tape, and 2.) measure w (acutal razor width) initially, which could be difficult to do accurately.

Actually the change in the hypotenuse is a second order effect, so it's negligible, the errors of the actual measurement are much larger.
The stretching of the tape can change the thickness significantly, so it is important to take a measurement with the actual tape on.



In any case I can do any calculation in octave much faster than anybody can do it in excel (programming it is faster, the data entry is faster, and i'd speculate that the negligible amount of compute time is faster too). It's more portable than anything else too, as I can give you a simple ascii file and unless having to have to buy excell or download a free alternative that is compatible with your file, the octave program is downloadable for free and it much smaller than say open office.

but since it is so efficient most people find the interface a bit too spartan to what they are used.

Originally Posted by gugi

since it is so efficient most people find the interface a bit too spartan to what they are used.

doesn't that produce a less efficient result for those people who have trouble using it?

Originally Posted by hoglahoo

doesn't that produce a less efficient result for those people who have trouble using it?

yes, in the same way the cartridge razors are a lot more efficient for those who lack the skills to use something better.