Tag Archives: Uncourse

Social Interest Positioning – Visualising Facebook Friends’ Likes With Data Grabbed Using Google Refine

What do my Facebook friends have in common in terms of the things they have Liked, or in terms of their music or movie preferences? (And does this say anything about me?!) Here’s a recipe for visualising that data…

After discovering via Martin Hawksey that the recent (December, 2011) 2.5 release of Google Refine allows you to import JSON and XML feeds to bootstrap a new project, I wondered whether it would be able to pull in data from the Facebook API if I was logged in to Facebook (Google Refine does run in the browser after all…)

Looking through the Facebook API documentation whilst logged in to Facebook, it’s easy enough to find exemplar links to things like your friends list (https://graph.facebook.com/me/friends?access_token=A_LONG_JUMBLE_OF_LETTERS) or the list of likes someone has made (https://graph.facebook.com/me/likes?access_token=A_LONG_JUMBLE_OF_LETTERS); replacing me with the Facebook ID of one of your friends should pull down a list of their friends, or likes, etc.

(Note that validity of the access token is time limited, so you can’t grab a copy of the access token and hope to use the same one day after day.)

Grabbing the link to your friends on Facebook is simply a case of opening a new project, choosing to get the data from a Web Address, and then pasting in the friends list URL:

Click on next, and Google Refine will download the data, which you can then parse as a JSON file, and from which you can identify individual record types:

If you click the highlighted selection, you should see the data that will be used to create your project:

You can now click on Create Project to start working on the data – the first thing I do is tidy up the column names:

We can now work some magic – such as pulling in the Likes our friends have made. To do this, we need to create the URL for each friend’s Likes using their Facebook ID, and then pull the data down. We can use Google Refine to harvest this data for us by creating a new column containing the data pulled in from a URL built around the value of each cell in another column:

The Likes URL has the form https://graph.facebook.com/me/likes?access_token=A_LONG_JUMBLE_OF_LETTERS which we’ll tinker with as follows:

The throttle control tells Refine how often to make each call. I set this to 500ms (that is, half a second), so it takes a few minutes to pull in my couple of hundred or so friends (I don’t use Facebook a lot;-). I’m not sure what limit the Facebook API is happy with (if you hit it too fast (i.e. set the throttle time too low), you may find the Facebook API stops returning data to you for a cooling down period…)?

Having imported the data, you should find a new column:

At this point, it is possible to generate a new column from each of the records/Likes in the imported data… in theory (or maybe not..). I found this caused Refine to hang though, so instead I exprted the data using the default Templating… export format, which produces some sort of JSON output…

I then used this Python script to generate a two column data file where each row contained a (new) unique identifier for each friend and the name of one of their likes:

import simplejson,csv

writer=csv.writer(open('fbliketest.csv','wb+'),quoting=csv.QUOTE_ALL)

fn='my-fb-friends-likes.txt'

data = simplejson.load(open(fn,'r'))
id=0
for d in data['rows']:
	id=id+1
	#'interests' is the column name containing the Likes data
	interests=simplejson.loads(d['interests'])
	for i in interests['data']:
		print str(id),i['name'],i['category']
		writer.writerow([str(id),i['name'].encode('ascii','ignore')])

[I think this R script, in answer to a related @mhawksey Stack Overflow question, also does the trick: R: Building a list from matching values in a data.frame]

I could then import this data into Gephi and use it to generate a network diagram of what they commonly liked:

Rather than returning Likes, I could equally have pulled back lists of the movies, music or books they like, their own friends lists (permissions settings allowing), etc etc, and then generated friends’ interest maps on that basis.

PS dropping out of Google Refine and into a Python script is a bit clunky, I have to admit. What would be nice would be to be able to do something like a “create new rows with new column from column” pattern that would let you set up an iterator through the contents of each of the cells in the column you want to generate the new column from, and for each pass of the iterator: 1) duplicate the original data row to create a new row; 2) add a new column; 3) populate the cell with the contents of the current iteration state. Or something like that…

PPS Related to the PS request, there is a sort of related feature in the 2.5 release of Google Refine that lets you merge data from across rows with a common key into a newly shaped data set: Key/value Columnize. Seeing this, it got me wondering what a fusion of Google Refine and RStudio might be like (or even just R support within Google Refine?)

PPPS this could be interesting – looks like you can test to see if a friendship exists given two Facebook user IDs.

Accessing and Visualising Sentencing Data for Local Courts

A recent provisional data release from the Ministry of Justice contains sentencing data from English(?) courts, at the offence level, for the period July 2010-June 2011: “Published for the first time every sentence handed down at each court in the country between July 2010 and June 2011, along with the age and ethnicity of each offender.” Criminal Justice Statistics in England and Wales [data]

In this post, I’ll describe a couple of ways of working with the data to produce some simple graphical summaries of the data using Google Fusion Tables and R…

…but first, a couple of observations:

– the web page subheading is “Quarterly update of statistics on criminal offences dealt with by the criminal justice system in England and Wales.”, but the sidebar includes the link to the 12 month set of sentencing data;
– the URL of the sentencing data is http://www.justice.gov.uk/downloads/publications/statistics-and-data/criminal-justice-stats/recordlevel.zip, which does not contain a time reference, although the data is time bound. What URL will be used if data for the period 7/11-6/12 is released in the same way next year?

The data is presented as a zipped CSV file, 5.4MB in the zipped form, and 134.1MB in the unzipped form.

The unzipped CSV file is too large to upload to a Google Spreadsheet or a Google Fusion Table, which are two of the tools I use for treating large CSV files as a database, so here are a couple of ways of getting in to the data using tools I have to hand…

Unix Command Line Tools

I’m on a Mac, so like Linux users I have ready access to a Console and several common unix commandline tools that are ideally suited to wrangling text files (on Windows, I suspect you need to install something like Cygwin; a search for windows unix utilities should turn up other alternatives too).

In Playing With Large (ish) CSV Files, and Using Them as a Database from the Command Line: EDINA OpenURL Logs and Postcards from a Text Processing Excursion I give a couple of examples of how to get started with some of the Unix utilities, which we can crib from in this case. So for example, after unzipping the recordlevel.csv document I can look at the first 10 rows by opening a console window, changing directory to the directory the file is in, and running the following command:

head recordlevel.csv

Or I can pull out rows that contain a reference to the Isle of Wight using something like this command:

grep -i wight recordlevel.csv > recordsContainingWight.csv

(The -i reads: “ignoring case”; grep is a command that identifies rows contain the search term (wight in this case). The > recordsContainingWight.csv says “send the result to the file recordsContainingWight.csv” )

Having extracted rows that contain a reference to the Isle of Wight into a new file, I can upload this smaller file to a Google Spreadsheet, or as Google Fusion Table such as this one: Isle of Wight Sentencing Fusion table.

Once in the fusion table, we can start to explore the data. So for example, we can aggregate the data around different values in a given column and then visualise the result (aggregate and filter options are available from the View menu; visualisation types are available from the Visualize menu):

We can also introduce filters to allow use to explore subsets of the data. For example, here are the offences committed by females aged 35+:

Looking at data from a single court may be of passing local interest, but the real data journalism is more likely to be focussed around finding mismatches between sentencing behaviour across different courts. (Hmm, unless we can get data on who passed sentences at a local level, and look to see if there are differences there?) That said, at a local level we could try to look for outliers maybe? As far as making comparisons go, we do have Court and Force columns, so it would be possible to compare Force against force and within a Force area, Court with Court?

R/RStudio

If you really want to start working the data, then R may be the way to go… I use RStudio to work with R, so it’s a simple matter to just import the whole of the reportlevel.csv dataset.

Once the data is loaded in, I can use a regular expression to pull out the subset of the data corresponding once again to sentencing on the Isle of Wight (i apply the regular expression to the contents of the court column:

recordlevel <- read.csv("~/data/recordlevel.csv") iw=subset(recordlevel,grepl("wight",court,ignore.case=TRUE))

We can then start to produce simple statistical charts based on the data. For example, a bar plot of the sentencing numbers by age group:

age=table(iw$AGE) barplot(age, main="IW: Sentencing by Age", xlab="Age Range")

We can also start to look at combinations of factors. For example, how do offence types vary with age?

ageOffence=table(iw$AGE, iw$Offence_type) barplot(ageOffence,beside=T,las=3,cex.names=0.5,main="Isle of Wight Sentences", xlab=NULL, legend = rownames(ageOffence))

If we remove the beside=T argument, we can produce a stacked bar chart:

barplot(ageOffence,las=3,cex.names=0.5,main="Isle of Wight Sentences", xlab=NULL, legend = rownames(ageOffence))

If we import the ggplot2 library, we have even more flexibility over the presentation of the graph, as well as what we can do with this sort of chart type. So for example, here’s a simple plot of the number of offences per offence type:

require(ggplot2) #You may need to install ggplot2 as a library if it isn't already installed ggplot(iw, aes(factor(Offence_type)))+ geom_bar() + opts(axis.text.x=theme_text(angle=-90))+xlab('Offence Type')

Alternatively, we can break down offence types by age:

ggplot(iw, aes(AGE))+ geom_bar() +facet_wrap(~Offence_type)

We can bring a bit of colour into a stacked plot that also displays the gender split on each offence:

ggplot(iw, aes(AGE,fill=sex))+geom_bar() +facet_wrap(~Offence_type)

One thing I’m not sure how to do is rip the data apart in a ggplot context so that we can display percentage breakdowns, so we could compare the percentage breakdown by offence type on sentences awarded to males vs. females, for example? If you do know how to do that, please post a comment below 😉

PS HEre’s an easy way of getting started with ggplot… use the online hosted version at http://www.yeroon.net/ggplot2/ using this data set: wightCrimRecords.csv; download the file to your computer then upload it as shown below:

PPS I got a little way towards identifying percentage breakdowns using a crib from here. The following command:
iwp=tapply(iw$Offence_type,iw$sex,function(x){prop.table(table(x))})
generates a (multidimensional) array for the responseVar (Offence) about the groupVar (sex). I don’t know how to generate a single data frame from this, but we can create separate ones for each sex as follows:
iwpMale=data.frame(iwp['Male']) iwpFemale=data.frame(iwp['Female'])
We can then plot these percentages using constructions of the form:
ggplot(iwp2)+geom_bar(aes(x=Male.x,y=Male.Freq))
What I haven’t worked out how to do is elegantly map from the multidimensional array to a single data.frame? If you know how, please add a comment below…(I also posted a question on Cross Validated, the stats bit of Stack Exchange…)

Visualising Twitter Friend Connections Using Gephi: An Example Using the @WiredUK Friends Network

To corrupt a well known saying, “cook a man a meal and he’ll eat it; teach a man a recipe, and maybe he’ll cook for you…”, I thought it was probably about time I posted the recipe I’ve been using for laying out Twitter friends networks using Gephi, not least because I’ve been generating quite a few network files for folk lately, giving them copies, and then not having a tutorial to point them to. So here’s that tutorial…

The starting point is actually quite a long way down the “how did you that?” chain, but I have to start somewhere, and the middle’s easier than the beginning, so that’s where we’ll step in (I’ll give some clues as to how the beginning works at the end…;-)

Here’s what we’ll be working towards: a diagram that shows how the people on Twitter that @wiredUK follows follow each other:

The tool we’re going to use to layout this graph from a data file is a free, extensible, open source, cross platform Java based tool called Gephi. If you want to play along, download the datafile. (Or try with a network of your own, such as your Facebook network.)

From the Gephi file menu, Open the appropriate graph file:

Import the file as a Directed Graph:

The Graph window displays the graph in a raw form:

Sometimes a graph may contain nodes that are not connected to any other nodes. (For example, protected Twitter accounts do not publish – and are not published in – friends or followers lists publicly via the Twitter API.) Some layout algorithms may push unconnected nodes far away from the rest of the graph, which can affect generation of presentation views of the network, so we need to filter out these unconnected nodes. The easiest way of doing this is to filter the graph using the Giant Component filter.

To colour the graph, I often make us of the modularity statistic. This algorithm attempts to find clusters in the graph by identifying components that are highly interconnected.

This algorithm is a random one, so it’s often worth running it several times to see how many communities typically get identified.

A brief report is displayed after running the statistic:

While we have the Statistics panel open, we can take the opportunity to run another measure: the HITS algorithm. This generates the well known Authority and Hub values which we can use to size nodes in the graph.

The next step is to actually colour the graph. In the Partition panel, refresh the partition options list and then select Modularity Class.

Choose appropriate colours (right click on each colour panel to select an appropriate colour for each class – I often select pastel colours) and apply them to the graph.

The next thing we want to do is lay out the graph. The Layout panel contains several different layout algorithms that can be used to support the visual analysis of the structures inherent in the network; (try some of them – each works in a slightly different way; some are also better than others for coping with large networks). For a network this size and this densely connected,I’d typically start out with one of the force directed layouts, that positions nodes according to how tightly linked they are to each other.

When you select the layout type, you will notice there are several parameters you can play with. The default set is often a good place to start…

Run the layout tool and you should see the network start to lay itself out. Some algorithms require you to actually Stop the layout algorithm; others terminate themselves according to a stopping criterion, or because they are a “one-shot” application (such as the Expansion algorithm, which just scales the x and y values by a given factor).

We can zoom in and out on the layout of the graph using a mouse wheel (on my MacBook trackpad, I use a two finger slide up and down), or use the zoom slider from the “More options” tab:

To see which Twitter ID each node corresponds to, we can turn on the labels:

This view is very cluttered – the nodes are too close to each other to see what’s going on. The labels and the nodes are also all the same size, giving the same visual weight to each node and each label. One thing I like to do is resize the nodes relative to some property, and then scale the label size to be proportional to the node size.

Here’s how we can scale the node size and then set the text label size to be proportional to node size. In the Ranking panel, select the node size property, and the attribute you want to make the size proportional to. I’m going to use Authority, which is a network property that we calculated when we ran the HITS algorithm. Essentially, it’s a measure of how well linked to a node is.

The min size/max size slider lets us define the minimum and maximum node sizes. By default, a linear mapping from attribute value to size is used, but the spline option lets us use a non-linear mappings.

I’m going with the default linear mapping…

We can now scale the labels according to node size:

Note that you can continue to use the text size slider to scale the size of all the displayed labels together.

This diagram is now looking quite cluttered – to make it easier to read, it would be good if we could spread it out a bit. The Expansion layout algorithm can help us do this:

A couple of other layout algorithms that are often useful: the Transformation layout algorithm lets us scale the x and y axes independently (compared to the Expansion algorithm, which scales both axes by the same amount); and the Clockwise Rotate and Counter-Clockwise Rotate algorithm lets us rotate the whole layout (this can be useful if you want to rotate the graph so that it fits neatly into a landscape view.

The expanded layout is far easier to read, but some of the labels still overlap. The Label Adjust layout tool can jiggle the nodes so that they don’t overlap.

(Note that you can also move individual nodes by clicking on them and dragging them.)

So – nearly there… The final push is to generate a good quality output. We can do this from the preview window:

The preview window is where we can generate good quality SVG renderings of the graph. The node size, colour and scaled label sizes are determined in the original Overview area (the one we were working in), although additional customisations are possible in the Preview area.

To render our graph, I just want to make a couple of tweaks to the original Default preview settings: Show Labels and set the base font size.

Click on the Refresh button to render the graph:

Oops – I overdid the font size… let’s try again:

Okay – so that’s a good start. Now I find I often enter into a dance between the Preview ad Overview panels, tweaking the layout until I get something I’m satisfied with, or at least, that’s half-way readable.

How to read the graph is another matter of course, though by using colour, sizing and placement, we can hopefully draw out in a visual way some interesting properties of the network. The recipe described above, for example, results in a view of the network that shows:

– groups of people who are tightly connected to each other, as identified by the modularity statistic and consequently group colour; this often defines different sorts of interest groups. (My follower network shows distinct groups of people from the Open University, and JISC, the HE library and educational technology sectors, UK opendata and data journalist types, for example.)
– people who are well connected in the graph, as displayed by node and label size.

Here’s my final version of the @wiredUK “inner friends” network:

You can probably do better though…;-)

To recap, here’s the recipe again:

– filter on connected component (private accounts don’t disclose friend/follower detail to the api key i use) to give a connected graph;
– run the modularity statistic to identify clusters; sometimes I try several attempts
– colour by modularity class identified in previous step, often tweaking colours to use pastel tones
– I often use a force directed layout, then Expansion to spread to network out a bit if necessary; the Clockwise Rotate or Counter-Clockwise rotate will rotate the network view; I often try to get a landscape format; the Transformation layout lets you expand or contract the graph along a single axis, or both axes by different amounts.
– run HITS statistic and size nodes by authority
– size labels proportional to node size
– use label adjust and expand to to tweak the layout
– use preview with proportional labels to generate a nice output graph
– iterate previous two steps to a get a layout that is hopefully not completely unreadable…

Got that?!;-)

Finally, to the return beginning. The recipe I use to generate the data is as follows:

grab a list of twitter IDs (call it L); there are several ways of doing this, for example: obtain a list of tweets on a particular topic by searching for a particular hashtag, then grab the set of unique IDs of people using the hashtag; grab the IDs of the members of one or more Twitter lists; grab the IDs of people following or followed by a particular person; grab the IDs of people sending geo-located tweets in a particular area;
for each person P in L, add them as a node to a graph;
for each person P in L, get a list of people followed by the corresponding person, e.g. Fr(P)
for each X in e.g. Fr(P): if X in Fr(P) and X in L, create an edge [P,X] and add it to the graph
save the graph in a format that can be visualised in Gephi.

To make this recipe, I use Tweepy and a Python script to call the Twitter API and get the friends lists from there, but you could use the Google Social API to get the same data. There’s an example of calling that API using Javscript in my “live” Twitter friends visualisation script (Using Protovis to Visualise Connections Between People Tweeting a Particular Term) as well as in the A Bit of NewsJam MoJo – SocialGeo Twitter Map.

Postcards from a Text Processing Excursion

It never ceases to amaze me how I lack even the most basic computer skills, but that’s one of the reasons I started this blog: to demonstrate and record my fumbling learning steps so that others maybe don’t have to spend so much time being as dazed and confused as I am most of the time…

Anyway, I spent a fair chunk of yesterday trying to find a way of getting started with grappling with CSV data text files that are just a bit too big to comfortably manage in a text editor or simple spreadsheet (so files over 50,000 or so rows, up to low millions) and that should probably be dumped into a database if that option was available, but for whatever reason, isn’t… (Not feeling comfortable with setting up and populating a database is one example…But I doubt I’ll get round to blogging my SQLite 101 for a bit yet…)

Note that the following tools are Unix tools – so they work on Linux and on a Mac, but probably not on Windows unless you install a unix tools package (such as GnuWin – coreutils and sed, which look good for starters…). Another alternative would be to download the Data Journalism Developer Studio and run it either as a bootable CD/DVD, or as a virtual machine using something like VMWare or VirtualBox.

All the tools below are related to the basic mechanics of wrangling with text files, which include CSV (comma separated) and TSV (tab separated) files. Your average unix jockey will look at you with sympathetic eyes if you rave bout them, but for us mere mortals, they may make life easier for you than you ever thought possible…

[If you know of simple tricks in the style of what follows that I haven’t included here, please feel free to add them in as a comment, and I’ll maybe try to work then into a continual updating of this post…]

If you want to play along, why not check out this openurl data from EDINA (data sample; a more comprehensive set is also available if you’re feeling brave: monthly openurl data).

So let’s start at the beginning and imagine your faced with a large CSV file – 10MB, 50MB, 100MB, 200MB large – and when you try to open it in your text editor (the file’s too big for Google spreadsheets and maybe even for Google Fusion tables) the whole thing just grinds to a halt, if doesn’t actually fall over.

What to do?

To begin with, you may want to take a deep breath and find out just what sort of beast you have to contend with. You know the file size, but what else might you learn? (I’m assuming the file has a csv suffix, L2sample.csv say, so for starters we’re assuming it’s a text file…)

The wc (word count) command is a handy little tool that will give you a quick overview of how many rows there are in the file:

wc -l L2sample.csv

I get the response 101 L2sample.csv, so there are presumably 100 data rows and 1 header row.

We can learn a little more by taking the -l linecount switch off, and getting a report back on the number of words and characters in the file as well:

wc L2sample.csv

Another thing that you might consider doing is just having a look at the structure of the file, by sampling the first few rows of it and having a peek at them. The head command can help you here.

head L2sample.csv

By default, it returns the first 10 rows of the file. IF we want to change the number of rows displayed, we can use the -n switch:

head -n 4 L2sample.csv

As well as the head command, there is the tail command; this can be used to peek at the lines at the end of the file:

tail L2sample.csv tail -n 15 L2sample.csv

When I look at the rows, I see they have the form:

logDate	logTime	encryptedUserIP	institutionResolverID	routerRedirectIdentifier ...
2011-04-04	00:00:03	kJJNjAytJ2eWV+pjbvbZTkJ19bk	715781	ukfed ...
2011-04-04	00:00:14	/DAGaS+tZQBzlje5FKsazNp2lhw	289516	wayf ...
2011-04-04	00:00:15	NJIy8xkJ6kHfW74zd8nU9HJ60Bc	569773	athens ...

So, not comma separated then; tab separated…;-)

If you were to upload a tab separated file to something like Google Fusion Tables, which I think currently only parses CSV text files for some reason, it will happily spend the time uploading the data – and then shove it into a single column.

I’m not sure if there are column splitting tools available in Fusion Tables – there weren’t last time I looked, though maybe we might expect a fuller range of import tools to appear at some point; many applications that accept text based data files allow you to specify the separator type, as for example in Google spreadsheets:

I’m personally living in hope that some sort of integration with the Google Refine data cleaning tool will appear one day…

If you want to take a sample of a large data file and put into another smaller file that you can play with or try things out with, the head (or tail) tool provides one way of doing that thanks to the magic of Unix redirection (which you might like to think of as a “pipe”, although that has a slightly different meaning in Unix land…). The words/jargon may sound confusing, and the syntax may look cryptic, but the effect is really powerful: take the output from a command and shove it into a file.

So, given a CSV file with a million rows, suppose we want to run a few tests in an application using a couple of hundred rows. This trick will help you generate the file containing the couple of hundred rows.

Here’s an example using L2sample.csv – we’ll create a file containing the first 20 rows, plus the header row:

head -n 21 L2sample.csv > subSample.csv

See the > sign? That says “take the output from the command on the left, and shove it into the file on the right”. (Note that if subSample.csv already exists, it will be overwritten, and you will lose the original.)

There’s probably a better way of doing this, but if you want to generate a CSV file (with headers) containing the last 10 rows, for example, of a file, you can use the cat command to join a file containing the headers with a file containing the last 10 rows:

head -n 1 L2sample.csv > headers.csv tail -n 20 L2sample.csv > subSample.csv cat headers.csv subSample.csv > subSampleWithHeaders.csv

(Note: don’t try to cat a file into itself, or Ouroboros may come calling…)

Another very powerful concept from the Unix command line is the notion of | (the pipe). This lets you take the output from one command and direct it to another command (rather than directing it into a file, as > does). So for example, if we want to extract rows 10 to 15 from a file, we can use head to grab the first 15 rows, then tail to grab the last 6 rows of those 15 rows (count them: 10, 11, 12, 13, 14, 15):

head -n 15 L2sample.csv | tail -n 6 > middleSample.csv

Try to read in as an English phrase (the | and > are punctuation): take the the first [head] 15 rows [-n 15] of the file L2sample.csv and use them as input [|] to the tail command; take the last [tail] 6 lines [-n 6] of the input data and save them [>] as the file middleSample.csv.

If we want to add in the headers, we can use the cat command:

cat headers.csv middleSample.csv > middleSampleWithHeaders.csv

We can use a pipe to join all sorts of commands. If our file only uses a single word for each column header, we can count the number of columns (single words) by grabbing the header row and sending it to wc, which will count the words for us:

head -n 1 L2sample.csv | wc

(Take the first row of L2sample.csv and count the lines/words/characters. If there is one word per column header, the word count gives us the column count…;-)

Sometimes we just want to split a big file into a set of smaller files. The split command is our frind here, and lets us split a file into smaller files containing up to a know number of rows/lines:

split -l 15 L2sample.csv subSamples

This will generate a series of files named subSamplesaa, subSamplesab, …, each containing 15 lines (except for the last one, which may contain less…).

Note that the first file will contain the header and 14 data rows, and the other files will contain 15 data rows but no column headings. To get round this, you might want to split on a file that doesn’t contain the header. (So maybe use wc -l to find the number of rows in the original file, create a header free version of the data by using tail on one less than the number of rows in the file, then split the header free version. You might then one to use cat to put the header back in to each of the smaller files…)

A couple of other Unix text processing tools let us use a CSV file as a crude database. The grep searches a file for a particular term or text pattern (known as a regular expression, which I’m not going to cover much in this post… suffice to note for now that you can do real text processing voodoo magic with regular expressions…;-)

So for example, in out test file, I can search for rows that contain the word mendeley

grep mendeley L2sample.csv

We can also redirect the output into a file:

grep EBSCO L2sample.csv > rowsContainingEBSCO.csv

If the text file contains columns that are separated by a unique delimiter (that is, some symbol that is only ever used to separate the columns), we can use the cut command to just pull out particular columns. The cut command assumes a tab delimiter (we can specify other delimiters explicitly if we need to), so we can use it on our testfile to pull out data from the third column in our test file:

cut -f 3 L2sample.csv

We can also pull out multiple columns and save them in a file:

cut -f 1,2,14,17 L2sample.csv > columnSample.csv

If you pull out just a single column, you can sort the entries to see what different entries are included in the column using the sort command:

cut -f 40 L2sample.csv | sort

(Take column 40 of the file L2sample.csv and sort the items.)

We can also take this sorted list and identify the unique entries using the uniq command; so here are the different entries in column 40 of our test file:

cut -f 40 L2sample.csv | sort | uniq

(Take column 40 of the file L2sample.csv, sort the items, and display the unique values.)

(The uniq command appears to make comparaisons between consecutive lines, hence the nee to sort first.)

The uniq command will also count the repeat occurrence of unique entries if we ask it nicely (-c):

cut -f 40 L2sample.csv | sort | uniq -c

(Take column 40 of the file L2sample.csv, sort the items, and display the unique values along with how many times they appear in the column as a whole.)

The final command I’m going to mention here is magic search and replace operator called sed. I’m aware that this post is already over long, so I’ll maybe return to this in a later post, aside from giving you a tease of scome scarey voodoo… how to convert a tab delimited file to a comma separated file. One recipe is given by Kevin Ashley as follows:

sed 's/"/\"/g; s/^/"/; s/$/"/; s/ctrl-V<TAB>/","/g;' origFile.tsv > newFile.csv

(See also this related question on #getTheData: Converting large-ish tab separated files to CSV.)

Note: if you have a small amount of text and need to wrangle it on some way, the Text Mechanic site might have what you need…

This lecture note on Unix Tools provides a really handy cribsheet of Unix command line text wrangling tools, though the syntax does appear to work for me using some of the commands as given their (the important thing is the idea of what’s possible…).

If you’re looking for regular expression helpers (I haven’t really mentioned these at all in this post, suffice to say they’re a mechanism for doing pattern based search and replace, and which in the right hands can look like real voodoo text processing magic!), check out txt2re and Regexpal (about regexpal).

TO DO: this is a biggie – the join command will join rows from two files with common elements in specified columns. I canlt get it working properly with my test files, so I’m not blogging it just yet, but here’s a starter for 10 if you want to try… Unix join examples