Basic Matrices in R

> # create a 4x3 matrix 
> a=matrix(c(1,2,3,4,5,6,7,8,9,10,11,12), nrow=4)
> a
     [,1] [,2] [,3]
[1,]    1    5    9
[2,]    2    6   10
[3,]    3    7   11
[4,]    4    8   12
> #arrange the numbers by row
> a=matrix(c(1,2,3,4,5,6,7,8,9,10,11,12), nrow=4, byrow=T)
> a
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    7    8    9
[4,]   10   11   12
> # Combine 2x2 matrix by row and column
> e = matrix(c(1,2,3,4),nrow=2)
> f = matrix(c(5,6,7,8),nrow=2)
> e
     [,1] [,2]
[1,]    1    3
[2,]    2    4
> f
     [,1] [,2]
[1,]    5    7
[2,]    6    8
> cbind(e,f)
     [,1] [,2] [,3] [,4]
[1,]    1    3    5    7
[2,]    2    4    6    8
> rbind(e,f)
     [,1] [,2]
[1,]    1    3
[2,]    2    4
[3,]    5    7
[4,]    6    8
> # Take a single digit subset from Matrix a Row 3 Column 2
> a[3,2]
[1] 8
> # Take a 2x3 subset of Matrix a, change the numbers and then combine back in to the original.
> a[c(3,4),c(1,2,3)]
     [,1] [,2] [,3]
[1,]    7    8    9
[2,]   10   11   12
> a[c(3,4),c(1,2,3)] = matrix(c(1,2,3,4,5,6),nrow=2)
> a
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6
[3,]    1    3    5
[4,]    2    4    6

Created by Pretty R at inside-R.org

More here

Artificial Intelligence - a new mode of learning

The internet is a disruptive technology that takes existing heirarchies and squishes, pounds and generally beats them into something new. Take for instance the press where traditional paper media is looking more anachronistic by the second and is set to be replaced by something which we're not really quite sure what it is yet.

The same process has hardly started in higher education but the more you think about it the generation that grew up learning everything online is going to find it weird to pay some institution £9,000 a year to set in a lecture hall when you can learn the same stuff online for free or alot less. University will still be a central feature of many people's lives as the desire to move out of home is a great one for many teenagers but for learning increasingly people are going to do that on the net.

Step forward Peter Norvig and Sebastian Thrun with their Introduction to Artificial Intelligence class which is the online version of the introduction to artificial intelligence class they run at Stanford. While the students there have to get dressed to learn stuff people who learn online can stay in our underpants while the we feast our minds on the same brainfood.

No this wont get you a Stanford degree but the Jeffery Archer's of the future will sure be putting STANFORD in as bigger letters as their CV's can cope with safe in the knowledge they avoided the earthquake risk of visiting California before the big one strikes. You also get to compete with the people who do go to Stanford. For people whose access to HE is restricted this is a great opportunity which should be extended as far as possible. Elites will be made more porous. Society will be less bound by results in examinations at the age of 18 that people really don't care about just a few years later. This is to cut a long story short a good thing.

So if you want to learn about all the interesting things that make up the field of artifical intelligence then why not sign up? It's free afterall.

Analyzing a Twitter hashtag with R

I've been wanting to have a go at this since reading this great post on the subject by Heuristic Andrew. When news broke that the Prime Minister's Director of Strategy had proposed to abolish maternity leave amongst other things twitter reacted with the mocking hashtag #blueskyhilton.

I decided on this hashtag because I thought it would be relatively short. The Twitter API only goes up to 1500 tweets anyway. In fact #blueskyhilton turns out to have had 240 mentions. Which is a great size to be starting with.

There are a few conclusions to be drawn:

1) On a technical aside I need to find a better way to cope with shortened URL's

2) I don't think we've reached the limits of what vizualisation can do in presenting the information. On Heuristic Andrew there is a cluster dendrogram plot which is fine for a statistically minded audience but the rest of the population might find it a little perplexing.

3) I need to find firmer lines between who is tweeting, what they are tweeting and retweets.

4) The focus of the tweets seems to come from a small number of users but that may be due to the small sample size. Off hand ideas from a political backroom boy that most voters don't recognise don't excite Twitter.

5) Not all Tweeters on an issue will use the same hashtag so I may need a wider range of search terms.

6) This type of analysis would benefit from proper scripts and repeat sampling.

7) The corner of Twitter that was involved in #blueskyhilton won't be sending any Christmas cards to No. 10.

Anyway here's most of the code I used. Don't forget you'll need the XML package. For some reason pretty R has turned <- into < Think I prefer ugly R.

> bsh.vectors <- character(0)
> for (page in c(1:15))
+ {
+ twitter_q <-URLencode('#blueskyhilton')
+ twitter_url = paste('http://search.twitter.com/search.atom?q=',twitter_q,'&rpp=100&page=', page, sep='')
+ bsh.xml <-xmlParseDoc(twitter_url, asText=F)
+  bsh.vector <-xpathSApply(bsh.xml,'//s:entry/s:title', xmlValue, namespaces =c('s'='http://www.w3.org/2005/Atom'))
+ bsh.vectors <- c(bsh.vector, bsh.vectors)
+ }
> length(bsh.vectors)
[1] 240
> install.packages('tm')
> require(tm)
Loading required package: tm
> bsh.corpus <-Corpus(VectorSource(bsh.vectors))
> bsh.corpus <-tm_map(bsh.corpus, tolower)
> my_stopwords <- c(stopwords('english'), '#blueskyhilton', 'blueskyhilton')
> bsh.corpus <- tm_map(bsh.corpus, removeWords, my_stopwords)
> bsh.corpus <- tm_map(bsh.corpus, removePunctuation)
> bsh.dtm <-TermDocumentMatrix(bsh.corpus)
> bsh.dtm
A term-document matrix (849 terms, 240 documents)

Non-/sparse entries: 1785/201975
Sparsity           : 99%
Maximal term length: 36
Weighting          : term frequency (tf)
> findFreqTerms(bsh.dtm, lowfreq=10)
[1] "abolish"          "archiebland"      "benefits"   
[4] "day"              "growth"           "hashtag"    
[7] "hilton"           "ideas"            "months"     
[10] "people"           "policy"           "psbook"     
[13] "steve"            "stevehiltontapes" "wednesday"  
[16] "week"       
> findAssocs(bsh.dtm, 'hilton', 0.20)
    hilton           steve           blood           brain
      1.00            0.98            0.43            0.43
   notices            alan      equivalent httpbitlyesdjf9
      0.43            0.36            0.36            0.36
   minimal       partridge         somalia       political
      0.36            0.36            0.36            0.32
       cut       phildyson        research            send
      0.31            0.31            0.31            0.31
     ideas         hashtag  jimthehedgehog            nine
      0.29            0.26            0.26            0.25
    senior         servant          supply
      0.25            0.25            0.22
> findAssocs(bsh.dtm, 'hilton', 0.10)
        hilton               steve               blood
          1.00                0.98                0.43
         brain             notices                alan
          0.43                0.43                0.36
    equivalent     httpbitlyesdjf9             minimal
          0.36                0.36                0.36
     partridge             somalia           political
          0.36                0.36                0.32
           cut           phildyson            research
          0.31                0.31                0.31
          send               ideas             hashtag
          0.31                0.29                0.26
jimthehedgehog                nine              senior
          0.26                0.25                0.25
       servant              supply         adambienkov
          0.25                0.22                0.18
          andy           automatic                born
          0.18                0.18                0.18
      calsberg             coulson      counterbalance
          0.18                0.18                0.18
     dangerous            director           fascistic
          0.18                0.18                0.18
       fucking                 hit     httpbitlyo9txpg
          0.18                0.18                0.18
 httpcoameekab       httpcoeaaligl              leaked
          0.18                0.18                0.18
          meme              minute               moron
          0.18                0.18                0.18
         plans            plonkers               quota
          0.18                0.18                0.18
        spawns            strategy              streak
          0.18                0.18                0.18
        stupid       thejamesdixon             twitter
          0.18                0.18                0.18
        months               civil            benefits
          0.17                0.16                0.14
   archiebland             cameron       comprehension
          0.13                0.13                0.11
       defying         politicians thestevehiltontapes
          0.11                0.11                0.11 

Created by Pretty R at inside-R.org

What Statistical Test Should I Use?

Here is a handy rough and ready guide to which statistical test you should use on your data. Yes the colours are bright. Yes it is a bit flowchartastic but as a revision resource I have found it useful.

Many a statistics student is grateful to the magnificent Andy Field and his Discovering Statistics Using SPSS, in particular page 822 in the 3rd edition. My revision aid uses the same information but presents it in a more digestible format.

Which Statistical Test?

How to win the Lottery with R

Firstly don't play the lottery! You're not going to win but I guess with lottery fever gripping the nation, the Euromillions jackpot is a 12X rollover standing at £154 million, this is as good a time as any to put R to one of its more practical uses. Choosing random lottery numbers.

Firstly don't use rnorm as it won't give you whole numbers instead use sample like i've set out below. You can also use it on other data not just numbers but that's outside the scope of this post.

sample(what we're sampling from in this case numbers 1 to 50, how many samples you want to take ie 5, whether you want to pick the same thing more than once being a lottery we don't)

For the Euromillions you need to sample twice once for the main numbers. 5 numbers between 1 and 50 and then again for the 2 stars. 2 numbers between 1 and 11. Anyway this is how to do it.

> lotto<-sample(1:50,5,replace=F) 
> lotto2<-sample(1:11,2,replace=F)
> lotto [1] 16 17  4 49 30
> lotto2 [1] 5 1

So will this actually help you to win the lottery? Alas not but by using random numbers you're less likely to choose a common combination of numbers and have to share the jackpot with all the other punters who love to use 1,2,3,4,5,6,7 and other similar common numerical choices.

More on choosing random numbers in R and in the VERY unlikely probability you do win you may need this Stuff Rich People Love

When the OECD met ggplot2

Click on the picture to see full size.

I wanted to have a go at some of the more advanced graphing available in R so that meant the ggplot2 which people keep going on about. I got the last 6 months growth figures off the OECD website for all the member countries that had produced the figures and kept throwing various combinations of R/ggplot2 code at it until I got what I wanted.

What I found was that like R with ggplot2 the learning curve is steep but it does give total control if you're prepared to spend the time on it. I still haven't worked out how to add the quartiles automatically but adding the horizontal lines I think worked better as I could make the outer ones dashed and finding the figures was easy enough quantile(GDP)

This is also the first time i've used R Studio and I have to say it's great perhaps I found it a little slow but it's such a pretty and helpful environment to work in I'm going to stick with it.

Anyway here is the code I ended up using.

ggplot(oecd2, aes(x=CC, y=GDP))
+ geom_text(aes(label=Country, x = CC, y = GDP),colour="black", size=5)
+ xlab("Country") + ylab("Growth as % GDP Change + Average & Quartiles")
+ opts(title = "Growth in OECD Countries (Q4 2010 - Q1 2011)")
+ geom_hline(yintercept=0.5,linetype=2)
+ geom_hline(yintercept=1.6,linetype=1)
+ geom_hline(yintercept=1.9,linetype=2)

Data Without Boarders - Doing Good With Data

You know what the internet's like. Someone gets a good idea and they tell their friends and they pass it on and before you know it you're getting email from someone in a country which makes you go something like "Suriname really that's in South America I thought it sounded quite Asian. Are we sure it's not next to Cambodia?"

Anyway I got a tweet from DataMiner UK which mentioned Data Without Boarders which sounded cool so I signed up for the email and below is what we all got back. Anyway if you're interested in this why not sign up as well?


Well that was awesomely unexpected.

What I thought would just be a casual blog post about a project I hoped to quietly roll out in the fall became a lightning rod for some of the most enthusiastic, engaged, and socially conscious data folk that I ever could have imagined. As of my writing this, over 300 of you have shown your interest in this initiative by signing up to stay in the loop on the Data Without Borders email list. Considering I envisioned 20 of us sitting around a borrowed office to tackle this problem, that turnout seems incredible to me. In addition, I've been getting emails from around the globe from people with amazing socially conscious tech projects and an unbridled enthusiasm for using tech and data to help others. To all of you, whether you’re an excel ninja working with disenfranchised communities or just an interested observer, thank you for signing up and getting involved.

Some quick updates on next steps:

New Website: We’ll be working to roll out a proper site in early July where NGOs / non-profits can submit their proposals and where data people, be they statisticians, hackers, or other, can get involved and learn about upcoming events / partnerships.

Kickoff Event – NY Hack Day: Our first event will likely take the form of a NY-based hack day slated for the fall, in which three selected organizations will present proposals for short-term projects they'd like assistance with (that we’ll help you plan out). We’ll then have local data folk come and help realize their visions or consult on other ways to tackle the problems. Of course there will probably be pizza and beer.

Other Kickoffs: Not in NY? Fear not! We ultimately plan for DWB to be a free exchange of data scientists, regardless of locale. As this is our first event, logistics dictate that we do something close to home, but we’re also looking into sponsoring similar events across the country / world (if you’re someone that could help us make that happen, get in touch!) Heck, if you’re inclined, feel free to throw your own and tell us how it goes. We can compare notes.

New Name for the Site: This may seem trivial, but the site needs a proper name. Data is already borderless, Data Scientists Without Borders is a mouthful and exclusive sounding, and I’ve heard rumor that other professions ‘without borders’ are very protective of trademark. So before this goes too far, suggest a name for this initiative by emailing datawithoutborders AT gmail.com with your clever titles. Right now I’m partial to DataCorps (thanks, Mike Dewar!), so feel free to +1 that if you’re feeling unimaginative.

Once again, thanks to everyone who’s shown interest in this cause and who wants to get involved. If you emailed me personally and I haven’t gotten back to yet, my apologies. I’m working my way through the list and will get back to you as soon as I can. Ping me at datawithoutborders AT gmail.com if you haven’t heard from me by the end of the week.

We’ll send another update when the site’s live and will send word as our kickoff event approaches. Thanks again for inspiring me, Internet, and we're looking forward to doing amazing things with you all.

Best,

Jake