h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I thought the matlab examples were just supposed to look very pretty.

You may (or may not) want to say that matlab is a multi-platform program so the same matlab programs can be run on all sorts of operating systems (various unix systems, ms windows, mac os x, linux).

Ok, I've added a sentence about the program not stopping, and I've added a bit about OS's with some links

Having been asked about vectorisation a short while ago, I'm going to add a section on it, and I might as well add some explanatory footnotes to the rest of the Entry while I'm at it.

All done

Entry: MATLAB - the Programming Language - A18023762
Author: Alex 'Tufty' Ashman [!] - U566116

Probably worth mentioning that the conjecture is that the algorithm is finitely possible, and that you wouldn't expect it to continue for ever - maybe a footnote?



Is this clear enough? I don't think you need to get into Euclidian n-spaces or anything, but how about describing a vector as a multi-dimensional or multi-coordinate number?

Icy

That any good?

I've just written some code to find the date for Easter - F79270?thread=3747377 - but I don't think it's worth including it in this Entry.

That ticks all the right boxes!

I don't know if your article needs any more examples, but if you're particularly proud of it, then you should put it in.

I've written an Excel program which draws a blancmange, but I thought I'd spare the outside world on this occasion.

Fair enough

Good stuff!

I think I'm possibly the only PhD student in my department who didn't use MATLAB, so I don't know a great deal, but here's a few things:

> licenses for it are quite costly, with the language having no close equivalent and being subject to copyright

You're right about the licenses being costly... but I know of languages that are a bit like MATLAB; the one that we used when demonstrating to undergrads was called octave - http://www.octave.org/ - I'm sure that MATLAB is much better than octave but I don't know enough about MATLAB in order to say exactly what is better about it.

> Notice that the multiply (.*) and divide (./) symbols are preceded by dots - this is to indicate standard multiplication and division as opposed to the more complex operations often used on matrices

What does the / symbol on its own actually do? I remember what \ does but that's about it.

I wondered whether you could link to a h2g2 entry on matrix multiplication but it seems as though there isn't an edited entry (GTBacchus started one at A895511, it seems)...

Do you know why vectorisation is much faster than the loop method? I've certainly been told this in the past but never been told why.

I shall have to write an entry on parallel programming and distributed computing when I've finally got my PhD written up.

Again, nice entry!

I think I've sorted everything out

Anything else need doing to this?

I am reading this while on my holiday, and enjoying it too (I am now concerned that I might be a ).

Be that as it may, here are some comments:

>>...applications. Its main application is...<<
just in order to remove one of the instances of 'application', I would suggest 'Its main use is...'

>>The program used to run the code is available for...<<
I would suggest simplifying this to 'MATLAB is available for...'
Along this line, I notice that you use the terms program, language, code and script somewhat interchangeably - at least it seems so to me. For clarity's sake and for her sanity as well, I might suggest that you settle on a hierarchy. For example, MATLAB and 'the language' for the 4th generation thing that you bought - 3rd or lower generation language for the underlying C or Fortran - script for what you type onto your screen - and code for machine code. Or whatever suits you. (I may be making a big deal out of nothing - feel free to ignore this point if it's merely tedious)

>>gained the attention of various fields<<
might suggest 'gained acceptance in various fields'<<

>>allowing the creation of innocent-looking scripts which can take hours on end to execute<<
I like this very much

you explain the symbols such as ';' but you may have left out '~='
is this 'not equal to'?

>>this is to indicate standard multiplication and division as opposed to the more complex operations often used on matrices<<
I would suggest replacing 'standard' with 'simple' and 'complex' with 'complicated'

>>function lacks any code to catch<<
Here I would replace the word 'code' with 'way' as an example of how you might just eliminate that word when possible.

>>which will not be treated as code<<
'which MATLAB will ignore'

Very good work

I enjoy that you chose the 3n+1 problem as an example (as opposed to the more common 'hello world' choice)

I notice in your printout in post 13, and in Gnomon's two examples in his 3n+1 entry that each case finally hits a number that is 2 to some power and then drives down to 1. So, perhaps one could try to prove the conjecture by determining the probability that multiplying by 3 and adding 1 will eventually arrive at a power of 2. When I say 'one', of course I mean 'one with a working brain' - a category into which I do not fit. I blame my misspent youth.

Sorted

Trust me, it's not that simple - I got through several sheets of paper before I realised. The problem is that x3+1 takes you to a power of 2 multiplied by a prime number or several prime numbers, and the series continues until the prime number the power of 2 is multiplied by becomes 2. Thus, any serious attempt at solving the problem would probably have to solve the great engima of prime numbers on the way.

Ah, I see. If prime numbers could speak, I think they would sound like eeyore, 'Oh, I do have a busy social life - why just the other day a mathematician bumped into me and said 'Oh bother''

Well, good Entry Prime Stuff!

Your Guide Entry has just been picked from Peer Review by one of our Scouts, and is now heading off into the Editorial Process, which ends with publication in the Edited Guide. We've therefore moved this Review Conversation out of Peer Review and to the entry itself.

If you'd like to know what happens now, check out the page on 'What Happens after your Entry has been Recommended?' at EditedGuide-Process. We hope this explains everything.

Thanks for contributing to the Edited Guide!

Fantastic, Alex - one accepted, and one on the FP

Well done!

Hey, Congratulations!