Created an AI for a contest

This year the journal freiesMagazin organized the third contest in a series. This time it’s about programming an AI for a predator-prey-like game. I just submitted my short solution.

As I said, it’s the third programming contest. The first one was about switching gems and in the second contest it was the goal to navigate a robot through a factory. I didn’t got the announce of the first one and missed the second one as a consequence of a lack of time. Hence it’s a premiere for me!

Citing their introduction:

Same procedure as every day: It is late in the evening and you're still sitting at your office desk and listening to some music. Suddenly a siren sounds through all rooms, the doors are closing automatically and you cannot open them anymore. A light green mist appears and some creepy shapes wander around the hall. Sometimes you really hate Mondays …

So, at the beginning of the game all programmed bots are in the same team. After some time one of them changes to the opposite team, trying to catch one of the other while the other ones are fleeing. Simple and clear. It’s running through sockets and the bot-programmers can win vouchers. More information can be found at their website.

On one hand I’m interested in socket programming since a while and on the other hand I’m of course interested in the voucher, so I decided to take part in the contest although there are enough other things to do for me. I agreed with myself to put about two days of work into it. In the end I worked about three days, but however, I could program about 365 more. If you take a look at the code it’s kept more or less simple and many functions aren’t in use. For example I track a motion profile of each opponent, but when I’m predator I don’t care about it. It would be more promising to predict a actual position of a prey (for example with neural networks or something like that) instead of searching without any profoundness. But this would go beyond my scope…

So lets see how many people are also joining this contest. The result will be published mid-January. At least I’m last, but that’s not wicked. I had a lot of fun and even learned something. That’s the main thing. It’s taking part that counts! ;-)

I attached my bot, it’s licensed under GPLv3. In some further articles I’ll explain some smart details of my code, I think some of them are quiet nice to know.

Download: Java: Repository @ GitHub (Please take a look at the man-page. Browse bugs and feature requests.)

Vim plugin for R

Just found a very nice plugin for using R in Vim. It’s unbelievable comfortable!

There are at least two ways to install it. If your are working on a Debian based distro you can use the .deb package provided by the author Jakson Alves de Aquino itself. On this site you’ll also find some smart screen shots. Another way is the installation by hand (I did so). Download the package, in your download directory type something like this:

mkdir -p ~/.vim 
unzip vim-r-plugin-*.zip -d ~/.vim

Yes, that’s it! To start an R session just open a R-file ( .R or .Rnw or .Rd ) with vim and type \\rf . To close the session type \\rq (not saving hist) or \rw (saving history). The handling needs to getting used to.. Here is a list of common commands from the documentation (might want to print them as a cheat sheet!?) :

  . Start R (default)                                    \\rf
  . Start R --vanilla                                    \\rv
  . Start R (custom)                                     \\rc
  . Close R (no save)                                    \\rq
  . Close R (save workspace)                             \\rw

  . File                                               \\aa
  . File (echo)                                        \\ae
  . File (open .Rout)                                  \\ao
  . Block (cur)                                        \\bb
  . Block (cur, echo)                                  \\be
  . Block (cur, down)                                  \\bd
  . Block (cur, echo and down)                         \\ba
  . Function (cur)                                     \\ff
  . Function (cur, echo)                               \\fe
  . Function (cur and down)                            \\fd
  . Function (cur, echo and down)                      \\fa
  . Selection                                          \\ss
  . Selection (echo)                                   \\se
  . Selection (and down)                               \\sd
  . Selection (echo and down)                          \\sa
  . Paragraph                                          \\pp
  . Paragraph (echo)                                   \\pe
  . Paragraph (and down)                               \\pd
  . Paragraph (echo and down)                          \\pa
  . Line                                                \\l
  . Line (and down)                                     \\d
  . Line (and new one)                                  \\q

  . List space                                         \\rl
  . Clear console                                      \\rr
  . Clear all                                          \\rm
  . Object (print)                                     \\rp
  . Object (names)                                     \\rn
  . Object (str)                                       \\rt
  . Arguments (cur)                                    \\ra
  . Example (cur)                                      \\re
  . Help (cur)                                         \\rh
  . Summary (cur)                                      \\rs
  . Plot (cur)                                         \\rg
  . Plot and summary (cur)                             \\rb
  . Update Object Browser                              \\ro
  . Set working directory (cur file path)              \\rd
  . Build R tags file                   :RBuildTags
  . Build omniList (loaded packages)    :RUpdateObjList
  . Build omniList (installed packages) :RUpdateObjListAll
  . Sweave (cur file)                                  \\sw
  . Sweave and PDF (cur file)                          \\sp
  . Go to next R chunk                                  gn
  . Go to previous R chunk                              gN

But if you got used to, it’s very handy! At the start-up it opens a new R-console (just close it, doesn’t matter) and you can send single lines, a block or a whole file to R (see the documentation). Every thing I tried worked really fine!

A small example in action is presented in the image. In an earlier post I explained how to produce such a title consisting of R objects and Greek letters.

I’ve attached the documentation of this plugin, first and foremost for me for cheating, but of course you’re allowed to use it also ;-)

Download: HTML: Vim-R-plugin documentation (Please take a look at the man-page. Browse bugs and feature requests.)

Open Research Computation

I want to announce a new scientific journal: Open Research Computation.

I think it sounds quiet interesting, citing their aims & scope:

Open Research Computation publishes peer reviewed articles that describe the development, capacities, and uses of software designed for use by researchers in any field. Submissions relating to software for use in any area of research are welcome as are articles dealing with algorithms, useful code snippets, as well as large applications or web services, and libraries. Open Research Computation differs from other journals with a software focus in its requirement for the software source code to be made available under an Open Source Initiative compliant license, and in its assessment of the quality of documentation and testing of the software. In addition to articles describing software Open Research Computation also welcomes submissions that review or describe developments relating to software based tools for research. These include, but are not limited to, reviews or proposals for standards, discussion of best practice in research software development, educational and support resources and tools for researchers that develop or use software based tools.

Looking forward…

You may also be interested in a more detailed announce: Can a journal make a difference? Let’s find out.

Value of an R object in an expression

Just wanted to create an expression, existing of some mathematical annotation and a value of an R object. Wasn’t that intuitive!

Each single goal is easy to reach, for example to combine a value of an R object with text just use paste :

> n = 5
> paste ("n=", n, "!")
[1] "n= 5 !"

To have a plot title with an \(\alpha_1\) you can use expression :

> plot(1:5, runif(5, 1, 4), main=expression("this is a " * alpha[1] * " example"))

But to let the the title of a plot contain objects and Greek letters isn’t that easy. Those of you who think it’s just about combining paste and expression might try it on their own and come back head-ached after few minutes of unsuccessful testings.

The problem is, that expression interprets chars as expression and not as object identifier, of course, how should it know whether you mean the var alpha or the Greek letter!? The solution is called substitute ! With substitute you can replace objects inline, here is a small example:

> var=10
> substitute(paste("here is the content: ", v), list(v=var))
paste("here is the content: ", 10)

You see, substitute got a list what to substitute and replaces the v in paste with the content of var . Run eval to evaluate to result:

> var=10
> eval(substitute(paste("here is the content: ", v), list(v=var)))
[1] "here is the content:  10"

Now it’s easy to create a more complex plot title:

> var=10
> plot(1:5, runif(5, 1, 4), main=substitute(paste("here ", lambda[1], "=", v, " and ", epsilon^2, "=", b, "!"), list(v=var, b=var^2)))

Go out and produce imposing graphs! (-;

Martin Scharm

stuff. just for the records.

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