R by example: mining Twitter for consumer attitudes towards airlines

R by example: mining Twitter for consumer
attitudes towards airlines

presented at the

Boston Predictive Analytics
MeetUp
by

Jeffrey Breen
President
Cambridge Aviation Research

jbreen@cambridge.aero

June 2011

Cambridge Aviation Research • 245 First Street • Suite 1800 • Cambridge, MA 02142 • cambridge.aero

© Copyright 2010 by Cambridge Aviation Research. All rights reserved.

Airlines top customer satisfaction... alphabetically

http://www.theacsi.org/ 3

Actually, they rank below the Post
Office and health insurers

4

which gives us plenty to listen to
Completely unimpressed with @continental or @united.
RT @dave_mcgregor: Poor communication, goofy reservations systems and
Publicly pledging to all to turn my trip into a mess.
never fly @delta again.
The worst airline ever.
U have lost my patronage @united #fail on wifi in red carpet clubs (too
forever due to ur slow), delayed flight, customer service in red
incompetence carpet club (too slow), hmmm do u see a trend?

@United Weather delays may not be your fault,
but you are in the customer service business.
It's atrocious how people are getting treated!
We were just told we are delayed 1.5 @SouthwestAir I know you don't make the
hrs & next announcement on @JetBlue - weather. But at least pretend I am not a
“We're selling headsets.” Way to bother when I ask if the delay will make
capitalize on our misfortune. miss my connection
@SouthwestAir
I hate you with every Hey @delta - you suck! Your prices
single bone in my body are over the moon & to move a flight
for delaying my flight by a cpl of days is $150.00. Insane. I
3 hours, 30mins before I hate you! U ruined my vacation!
was supposed to board.
#hate

Game Plan
Search Twitter for
airline mentions &
collect tweet text Score sentiment for Summarize for each
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
Scrape ACSI web site for
airline customer satisfaction
scores

14

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

15

Searching Twitter in one line
R’s XML and RCurl packages make it easy to grab web data, but Jeff
Gentry’s twitteR package makes searching Twitter almost too easy:

> # load the package
> library(twitteR)
> # get the 1,500 most recent tweets mentioning ‘@delta’:
> delta.tweets = searchTwitter('@delta', n=1500)

See what we got in return: A “list” in R is a collection of
objects and its elements may be
> length(delta.tweets) named or just numbered.
[1] 1500
> class(delta.tweets)
[1] "list"
“[[ ]]” is used to access elements.

Examine the output
Let’s take a look at the ﬁrst tweet in the output list:

> tweet = delta.tweets[[1]]
tweet is an object of type “status”
from the “twitteR” package.
> class(tweet)
[1] "status"
attr(,"package") It holds all the information about
[1] "twitteR" the tweet returned from Twitter.

The help page (“?status”) describes some accessor methods like
getScreenName() and getText() which do what you would expect:

> tweet$getScreenName()
[1] "Alaqawari"
> tweet$getText()
[1] "I am ready to head home. Inshallah will try to get on the earlier
flight to Fresno. @Delta @DeltaAssist"

Extract the tweet text
R has several (read: too many) ways to apply functions iteratively.
•The plyr package uniﬁes them all with a consistent naming convention.
•The function name is determined by the input and output data types. We
have a list and would like a simple array output, so we use “laply”:

> delta.text = laply(delta.tweets, function(t) t$getText() )

> length(delta.text)[1] 1500
> head(delta.text, 5)
[1] "I am ready to head home. Inshallah will try to get on the earlier
flight to Fresno. @Delta @DeltaAssist"
[2] "@Delta Releases 2010 Corporate Responsibility Report - @PRNewswire
(press release) : http://tinyurl.com/64mz3oh"
[3] "Another week, another upgrade! Thanks @Delta!"
[4] "I'm not able to check in or select a seat for flight DL223/KL6023 to
Seattle tomorrow. Help? @KLM @delta"
[5] "In my boredom of waiting realized @deltaairlines is now @delta
seriously..... Stil waiting and your not even unloading status yet"

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

19

Estimating Sentiment

There are many good papers and resources describing methods to
estimate sentiment. These are very complex algorithms.

For this tutorial, we use a very simple algorithm which assigns a score by
simply counting the number of occurrences of “positive” and “negative”
words in a tweet. The code for our score.sentiment() function can be
found at the end of this deck.

Hu & Liu have published an “opinion lexicon” which categorizes
approximately 6,800 words as positive or negative and which can be
downloaded.

Positive: love, best, cool, great, good, amazing
Negative: hate, worst, sucks, awful, nightmare
20

Load sentiment word lists
1. Download Hu & Liu’s opinion lexicon:

http://www.cs.uic.edu/~liub/FBS/sentiment-analysis.html

2. Loading data is one of R’s strengths. These are simple text ﬁles,
though they use “;” as a comment character at the beginning:

> hu.liu.pos = scan('../data/opinion-lexicon-English/positive-
words.txt', what='character', comment.char=';')

> hu.liu.neg = scan('../data/opinion-lexicon-English/negative-
words.txt', what='character', comment.char=';')

3. Add a few industry-speciﬁc and/or especially emphatic terms:

> pos.words = c(hu.liu.pos, 'upgrade') The c() function
> neg.words = c(hu.liu.neg, 'wtf', 'wait', combines objects
'waiting', 'epicfail', 'mechanical') into vectors or lists

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

22

Algorithm sanity check
> sample = c("You're awesome and I love you",
"I hate and hate and hate. So angry. Die!",
"Impressed and amazed: you are peerless in your achievement of
unparalleled mediocrity.")
> result = score.sentiment(sample, pos.words, neg.words)
> class(result)
data.frames hold tabular data so they
[1] "data.frame"
consist of columns & rows which can
> result$score
be accessed by name or number.
[1] 2 -5 4
Here, “score” is the name of a column.

So, not so good with sarcasm. Here are a couple of real tweets:

> score.sentiment(c("@Delta I'm going to need you to get it together.
Delay on tarmac, delayed connection, crazy gate changes... #annoyed",
"Surprised and happy that @Delta helped me avoid the 3.5 hr layover I
was scheduled for. Patient and helpful agents. #remarkable"),
pos.words, neg.words)$score
[1] -4 5

Accessing data.frames
Here’s the data.frame just returned from score.sentiment():
> result
score text

1 2 You're awesome and I love you

2 -5 I hate and hate and hate. So angry. Die!

3 4 Impressed and amazed: you are peerless in your achievement of unparalleled mediocrity.

Elements can be accessed by name or position, and positions can be
ranges:
> result[1,1]
[1] 2
> result[1,'score']
[1] 2
> result[1:2, 'score']
[1] 2 -5
> result[c(1,3), 'score']
[1] 2 4
> result[,'score']
[1] 2 -5 4

Score the tweets
To score all of the Delta tweets, just feed their text into
score.sentiment():

> delta.scores = score.sentiment(delta.text, pos.words, Progress bar
neg.words, .progress='text') provided by
|==================================================| 100% plyr

Let’s add two new columns to identify the airline for when we
combine all the scores later:
> delta.scores$airline = 'Delta'
> delta.scores$code = 'DL’

Plot Delta’s score distribution
R’s built-in hist() function will create and plot histograms of your data:
> hist(delta.scores$score)

The ggplot2 alternative
ggplot2 is an alternative graphics package which generates more reﬁned
graphics:
> qplot(delta.scores$score)

Lather. Rinse. Repeat
To see how the other airlines fare, collect & score tweets for other
airlines.

Then combine all the results into a single “all.scores” data.frame:

> all.scores = rbind( american.scores, continental.scores, delta.scores,
jetblue.scores, southwest.scores, united.scores, us.scores )

rbind() combines
rows from
data.frames, arrays,
and matrices

Compare score distributions
ggplot2 implements “grammar of graphics”, building plots in layers:
> ggplot(data=all.scores) + # ggplot works on data.frames, always
geom_bar(mapping=aes(x=score, fill=airline), binwidth=1) +
facet_grid(airline~.) + # make a separate plot for each airline
theme_bw() + scale_fill_brewer() # plain display, nicer colors

ggplot2’s faceting
capability makes it
easy to generate the
same graph for
different values of a
variable, in this case
“airline”.

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

30

Ignore the middle
Let’s focus on very negative (<-2) and positive (>2) tweets:
> all.scores$very.pos = as.numeric( all.scores$score >= 2 )
> all.scores$very.neg = as.numeric( all.scores$score <= -2 )

For each airline ( airline + code ), let’s use the ratio of very positive to
very negative tweets as the overall sentiment score for each airline:
> twitter.df = ddply(all.scores, c('airline', 'code'), summarise,
pos.count = sum( very.pos ), neg.count = sum( very.neg ) )
> twitter.df$all.count = twitter.df$pos.count + twitter.df$neg.count
> twitter.df$score = round( 100 * twitter.df$pos.count /
twitter.df$all.count )

Sort with orderBy() from the doBy package:
> orderBy(~-score, twitter.df)

Any relation to ACSI’s airline scores?

http://www.theacsi.org/index.php?option=com_content&view=article&id=147&catid=&Itemid=212&i=Airlines

18

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

33

Scrape, don’t type
XML package provides amazing readHTMLtable() function:
> library(XML)
> acsi.url = 'http://www.theacsi.org/index.php?
option=com_content&view=article&id=147&catid=&Itemid=212&i=Airlines'
> acsi.df = readHTMLTable(acsi.url, header=T, which=1,
stringsAsFactors=F)
> # only keep column #1 (name) and #18 (2010 score)
> acsi.df = acsi.df[,c(1,18)]
> head(acsi.df,1)
10
1 Southwest Airlines 79

Well, typing metadata is OK, I guess... clean up column names, etc:

> colnames(acsi.df) = c('airline', 'score') NA (as in “n/a”) is
> acsi.df$code = c('WN', NA, 'CO', NA, 'AA', 'DL', supported as a
'US', 'NW', 'UA') valid value
> acsi.df$score = as.numeric(acsi.df$score) everywhere in R.

Game Plan
Search Twitter for
airline mentions &
each tweet airline
Load sentiment
word lists

Compare Twitter
sentiment with ACSI
satisfaction score
scores

35

Join and compare
merge() joins two data.frames by the specified “by=” fields. You can
specify ‘suffixes’ to rename conflicting column names:

> compare.df = merge(twitter.df, acsi.df, by='code',
suffixes=c('.twitter', '.acsi'))

Unless you specify “all=T”, non-matching rows are dropped (like a SQL
INNER JOIN), and that’s what happened to top scoring JetBlue.

With a very low score, and low traffic to boot, soon-to-disappear
Continental looks like an outlier. Let’s exclude:
> compare.df = subset(compare.df, all.count > 100)

an actual result!
ggplot will even run lm() linear
(and other) regressions for you
with its geom_smooth() layer:

> ggplot( compare.df ) +
geom_point(aes(x=score.twitter,
y=score.acsi,
color=airline.twitter), size=5) +
geom_smooth(aes(x=score.twitter,
y=score.acsi, group=1), se=F,
method="lm") +
theme_bw() +
opts(legend.position=c(0.2,
0.85))

37
21

http://www.despair.com/cudi.html

R code for example scoring function
score.sentiment = function(sentences, pos.words, neg.words, .progress='none')
{
require(plyr)
require(stringr)

# we got a vector of sentences. plyr will handle a list or a vector as an "l" for us
# we want a simple array of scores back, so we use "l" + "a" + "ply" = laply:
scores = laply(sentences, function(sentence, pos.words, neg.words) {

# clean up sentences with R's regex-driven global substitute, gsub():
sentence = gsub('[[:punct:]]', '', sentence)
sentence = gsub('[[:cntrl:]]', '', sentence)
sentence = gsub('d+', '', sentence)
# and convert to lower case:
sentence = tolower(sentence)

# split into words. str_split is in the stringr package
word.list = str_split(sentence, 's+')
# sometimes a list() is one level of hierarchy too much
words = unlist(word.list)

# compare our words to the dictionaries of positive & negative terms
pos.matches = match(words, pos.words)
neg.matches = match(words, neg.words)

# match() returns the position of the matched term or NA
# we just want a TRUE/FALSE:
pos.matches = !is.na(pos.matches)
neg.matches = !is.na(neg.matches)

# and conveniently enough, TRUE/FALSE will be treated as 1/0 by sum():
score = sum(pos.matches) - sum(neg.matches)

return(score)
}, pos.words, neg.words, .progress=.progress )

scores.df = data.frame(score=scores, text=sentences)
return(scores.df)
} 39

R by example: mining Twitter for consumer attitudes towards airlines

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