clustext is a collection of optimized tools for clustering text data via various text appropriate clustering algorithms. There are many great R clustering tools to locate topics within documents. I have had success with hierarchical clustering for topic extraction. This initial success birthed the hclustext package. Additional techniques such as kmeans and non-negative matrix factorization also proved useful. These algorithms began to be collected in a consistent manor of use in the clustext package. This package wraps many of the great R tools for clustering and working with sparse matrices to aide in the workflow associated with topic extraction.
The general idea is that we turn the documents into a matrix of words.
After this we weight the terms by importance using
tf-idf.
This helps the more salient words to rise to the top. Some clustering
algorithms require a similarity matrix while others require just the
tf-idf weighted DocumentTermMatrices. Likewise, some algorithms require
k terms to be specified before the model fit while others allow k
topics to be determined after the model has been fit.
With algorithms that require a similarity matrix (e.g., hierarchical
clustering) we apply cosine distance measures to compare the terms (or
features) of each document. I have found cosine distance to work well
with sparse matrices to produce distances metrics between the documents.
The clustering model is fit to separate the documents into clusters. In
the case of some clustering techniques (e.g., hierarchical clustering)
the user then may apply k clusters to the fit, clustering documents with
similar important text features. Other techniques require that k be
specified prior to fitting the model. The documents can then be grouped
by clusters and their accompanying salient words extracted as well.
The main functions, task category, & descriptions are summarized in the table below:
| Function | Category | Description |
|---|---|---|
data_store |
data structure | clustext's data structure (list of dtm + text) |
hierarchical_cluster |
cluster fit | Fits a hierarchical cluster model |
kmeans_cluster |
cluster fit | Fits a kmeans cluster model |
skmeans_cluster |
cluster fit | Fits an skmeans cluster model |
nfm_cluster |
cluster fit | Fits a non-negative matrix factorization cluster model |
assign_cluster |
assignment | Assigns cluster to document/text element |
get_text |
extraction | Get text from various clustext objects |
get_dtm |
extraction | Get tm::DocumentTermMatrix from various clustext objects |
get_removed |
extraction | Get removed text elements from various clustext objects |
get_documents |
extraction | Get clustered documents from an assign_cluster object |
get_terms |
extraction | Get clustered weighted important terms from an assign_cluster object |
as_topic |
categorization | View get_terms object as topics (pretty printed important words) |
write_cluster_text |
categorization | Write get_text(assign_cluster(myfit)) to file for human coding |
read_cluster_text |
categorization | Read in a human coded write_cluster_text file |
categorize |
categorization | Assign human categories and matching clusters to original data |
To download the development version of clustext:
Download the zip
ball or tar
ball, decompress
and run R CMD INSTALL on it, or use the pacman package to install
the development version:
if (!require("pacman")) install.packages("pacman")
pacman::p_load_gh(
"trinker/textshape",
"trinker/gofastr",
"trinker/termco",
"trinker/clustext"
)
You are welcome to:
- submit suggestions and bug-reports at: https://github.com/trinker/clustext/issues
- send a pull request on: https://github.com/trinker/clustext/
- compose a friendly e-mail to: tyler.rinker@gmail.com
if (!require("pacman")) install.packages("pacman")
pacman::p_load(clustext, dplyr, textshape, ggplot2, tidyr)
data(presidential_debates_2012)
The data structure for clustext is very specific. The data_storage
produces a DocumentTermMatrix which maps to the original text. The
empty/removed documents are tracked within this data structure, making
subsequent calls to cluster the original documents and produce weighted
important terms more robust. Making the data_storage object is the
first step to analysis.
We can give the DocumentTermMatrix rownames via the doc.names
argument. If these names are not unique they will be combined into a
single document as seen below. Also, if you want to do stemming, minimum
character length, stopword removal or such this is when/where it's done.
ds <- with(
presidential_debates_2012,
data_store(dialogue, doc.names = paste(person, time, sep = "_"))
)
ds
## <<Data Store (documents: 10, terms: 3,180)>>
## Text Elements : 10
## Elements Removed : 0
## Non-/sparse entries: 6916/24884
## Sparsity : 78%
## Maximal term length: 16
## Minimum term length: 3
Next we can fit a hierarchical cluster model to the data_store object
via hierarchical_cluster.
myfit <- hierarchical_cluster(ds)
myfit
##
## Call:
## fastcluster::hclust(d = distmes(x[["dtm"]]), method = method)
##
## Cluster method : ward.D
## Number of objects: 10
This object can be plotted with various k or h parameters specified
to experiment with cutting the dendrogram. This cut will determine the
number of clusters or topics that will be generated in the next step.
The visual inspection allows for determining how to cluster the data as
well as determining if a tf-idf, cosine, hierarchical cluster model is a
right fit for the data and task. By default plot uses an approximation
of k based on Can & Ozkarahan's (1990) formula (m * n)/t where
m and n are the dimensions of the matrix and t is the length of
the non-zero elements in matrix A.
- Can, F., Ozkarahan, E. A. (1990). Concepts and effectiveness of the cover-coefficient-based clustering methodology for text databases. ACM Transactions on Database Systems 15 (4): 483. doi:10.1145/99935.99938
Interestingly, in the plots below where k = 6 clusters, the model
groups each of the candidates together at each of the debate times.
plot(myfit)
##
## k approximated to: 5
plot(myfit, k=6)
plot(myfit, h = .75)
The assign_cluster function allows the user to dictate the number of
clusters. Because the model has already been fit the cluster assignment
is merely selecting the branches from the dendrogram, and is thus very
quick. Unlike many clustering techniques the number of clusters is done
after the model is fit, this allows for speedy cluster assignment,
meaning the user can experiment with the number of clusters.
ca <- assign_cluster(myfit, k = 6)
ca
## CROWLEY_time 2 LEHRER_time 1 OBAMA_time 1 OBAMA_time 2
## 1 2 3 4
## OBAMA_time 3 QUESTION_time 2 ROMNEY_time 1 ROMNEY_time 2
## 5 6 3 4
## ROMNEY_time 3 SCHIEFFER_time 3
## 5 2
To check the number of documents loading on a cluster there is a
summary method for assign_cluster which provides a descending data
frame of clusters and counts. Additionally, a horizontal bar plot shows
the document loadings on each cluster.
summary(ca)
## cluster count
## 1 2 2
## 2 3 2
## 3 4 2
## 4 5 2
## 5 1 1
## 6 6 1
The user can grab the texts from the original documents grouped by
cluster using the get_text function. Here I demo a 40 character
substring of the document texts.
get_text(ca) %>%
lapply(substring, 1, 40)
## $`1`
## [1] "Good evening from Hofstra University in "
##
## $`2`
## [1] "We'll talk about specifically about heal"
## [2] "Good evening from the campus of Lynn Uni"
##
## $`3`
## [1] "Jim, if I if I can just respond very qui"
## [2] "What I support is no change for current "
##
## $`4`
## [1] "Jeremy, first of all, your future is bri"
## [2] "Thank you, Jeremy. I appreciate your you"
##
## $`5`
## [1] "Well, my first job as commander in chief"
## [2] "Thank you, Bob. And thank you for agreei"
##
## $`6`
## [1] "Mister President, Governor Romney, as a "
As with many topic clustering techniques, it is useful to get the to
salient terms from the model. The get_terms function uses the
min-max
scaled, tf-idf weighted,
DocumentTermMatrix to extract the most frequent salient terms. These
terms can give a sense of the topic being discussed. Notice the absence
of clusters 1 & 6. This is a result of only a single document included
in each of the clusters. The term.cutoff hyperparmeter sets the lower
bound on the min-max scaled tf-idf to accept. If you don't get any terms
you may want to lower this or reduce min.n. Likewise, these two
parameters can be raised to eliminate noise.
get_terms(ca)
## $`1 (n=1)`
## term weight
## 1 mister 1.0000000
## 2 along 0.7086841
## 3 sort 0.6678306
## 4 unemployed 0.6223915
##
## $`2 (n=2)`
## term weight
## 1 segment 1.0000000
## 2 minutes 0.9091730
## 3 minute 0.6648988
##
## $`3 (n=2)`
## term weight
## 1 insurance 1.0000000
## 2 health 0.6200389
##
## $`4 (n=2)`
## term weight
## 1 coal 1.0000000
## 2 jobs 0.9439400
## 3 sure 0.9330092
## 4 immigration 0.9134630
## 5 oil 0.9014907
## 6 issue 0.7352300
## 7 candy 0.7303597
## 8 production 0.7291683
## 9 women 0.7073096
## 10 million 0.6792076
## 11 settle 0.6056192
## 12 illegally 0.6055244
##
## $`5 (n=2)`
## term weight
## 1 nuclear 1.0000000
## 2 iran 0.9511527
## 3 sanctions 0.8585336
## 4 israel 0.7895173
## 5 sure 0.7698270
## 6 region 0.7608304
## 7 military 0.7272537
## 8 troops 0.6768143
## 9 pakistan 0.6766784
## 10 world 0.6716568
## 11 threat 0.6520238
## 12 iraq 0.6467488
##
## $`6 (n=1)`
## term weight
## 1 department 1.0000000
## 2 chu 0.6666667
## 3 stated 0.6666667
## 4 misperception 0.6666667
Or pretty printed...
get_terms(ca) %>%
as_topic()
## Cluster 2 (n=2): segment, minutes, minute
## Cluster 3 (n=2): insurance, health
## Cluster 4 (n=2): coal, jobs, sure, immigration, oil, issue, candy, production...
## Cluster 5 (n=2): nuclear, iran, sanctions, israel, sure, region, military, troops...
## Cluster 1 (n=1): mister, along, sort, unemployed
## Cluster 6 (n=1): department, chu, stated, misperception
Here I plot the clusters, terms, and documents (grouping variables) together as a combined heatmap. This can be useful for viewing & comparing what documents are clustering together in the context of the cluster's salient terms. This example also shows how to use the cluster terms as a lookup key to extract probable salient terms for a given document.
key <- data_frame(
cluster = 1:6,
labs = get_terms(ca) %>%
tidy_list("cluster") %>%
select(-weight) %>%
group_by(cluster) %>%
summarize(term=paste(term, collapse=", ")) %>%
apply(1, paste, collapse=": ")
)
ca %>%
tidy_vector("id", "cluster") %>%
separate(id, c("person", "time"), sep="_") %>%
tbl_df() %>%
left_join(key, by = "cluster") %>%
mutate(n = 1) %>%
mutate(labs = factor(labs, levels=rev(key[["labs"]]))) %>%
unite("time_person", time, person, sep="\n") %>%
select(-cluster) %>%
complete(time_person, labs) %>%
mutate(n = factor(ifelse(is.na(n), FALSE, TRUE))) %>%
ggplot(aes(time_person, labs, fill = n)) +
geom_tile() +
scale_fill_manual(values=c("grey90", "red"), guide=FALSE) +
labs(x=NULL, y=NULL)
The get_documents function grabs the documents associated with a
particular cluster. This is most useful in cases where the number of
documents is small and they have been given names.
get_documents(ca)
## $`1`
## [1] "CROWLEY_time 2"
##
## $`2`
## [1] "LEHRER_time 1" "SCHIEFFER_time 3"
##
## $`3`
## [1] "OBAMA_time 1" "ROMNEY_time 1"
##
## $`4`
## [1] "OBAMA_time 2" "ROMNEY_time 2"
##
## $`5`
## [1] "OBAMA_time 3" "ROMNEY_time 3"
##
## $`6`
## [1] "QUESTION_time 2"
I like working in a chain. In the setup below we work within a
magrittr pipeline to fit a model, select clusters, and examine the
results. In this example I do not condense the 2012 Presidential Debates
data by speaker and time, rather leaving every sentence as a separate
document. On my machine the initial data_store and model fit take ~5-8
seconds to run. Note that I do restrict the number of clusters (for
texts and terms) to a random 5 clusters for the sake of space.
.tic <- Sys.time()
myfit2 <- presidential_debates_2012 %>%
with(data_store(dialogue)) %>%
hierarchical_cluster()
difftime(Sys.time(), .tic)
## Time difference of 5.450191 secs
## View Document Loadings
ca2 <- assign_cluster(myfit2, k = 100)
summary(ca2) %>%
head(12)
## cluster count
## 1 2 1409
## 2 25 54
## 3 15 50
## 4 39 46
## 5 61 39
## 6 36 37
## 7 40 33
## 8 17 31
## 9 31 29
## 10 37 28
## 11 27 25
## 12 46 23
## Split Text into Clusters
set.seed(5); inds <- sort(sample.int(100, 5))
get_text(ca2)[inds] %>%
lapply(head, 10)
## $`11`
## [1] "Yeah, we're going to yeah, I want to get to it."
## [2] "And do you yeah."
## [3] "Yeah, you bet."
## [4] "Yeah."
##
## $`21`
## [1] "Regulation is essential."
## [2] "You can't have a free market work if you don't have regulation."
## [3] "Every free economy has good regulation."
## [4] "You have to have regulation."
## [5] "Now, it wasn't just on Wall Street."
## [6] "We stepped in and had the toughest reforms on Wall Street since the one thousand nine hundred thirtys."
## [7] "And so the question is: Does anybody out there think that the big problem we had is that there was too much oversight and regulation of Wall Street?"
## [8] "Look, we have to have regulation on Wall Street."
## [9] "That's why I'd have regulation."
## [10] "I committed that I would rein in the excesses of Wall Street, and we passed the toughest Wall Street reforms since the one thousand nine hundred thirtys."
##
## $`28`
## [1] "We said you've got banks, you've got to raise your capital requirements."
## [2] "Well, actually it's it's it's a lengthy description."
## [3] "Well, actually Governor, that isn't what your plan does."
## [4] "Number two, we've got to make sure that we have the best education system in the world."
## [5] "We've got to reduce our deficit, but we've got to do it in a balanced way."
## [6] "I got to I got to move you on."
## [7] "He actually got|"
## [8] "He actually got the first question."
## [9] "Governor Romney, I'm sure you've got a reply there."
## [10] "I've got to say|"
##
## $`68`
## [1] "That's how we went after Al Qaida and bin Laden."
## [2] "I said that we'd go after al Qaeda and bin Laden, we have."
## [3] "I congratulate him on on taking out Osama bin Laden and going after the leadership in al Qaeda."
## [4] "When it comes to going after Osama bin Laden, you said, well, any president would make that call."
## [5] "And she said to me, You know, by finally getting bin Laden, that brought some closure to me."
## [6] "We had to go in there to get Osama bin Laden."
## [7] "Well, keep in mind our strategy wasn't just going after bin Laden."
##
## $`90`
## [1] "And finally, championing small business."
## [2] "And then let's take the last one, championing small business."
## [3] "I came through small business."
## [4] "I understand how hard it is to start a small business."
## [5] "I want to keep their taxes down on small business."
## [6] "So if you're starting a business, where would you rather start it?"
## [7] "But, of course, if you're a small business or a mom and pop business or a big business starting up here, you've got to pay even the reduced rate that Governor Romney's talking about."
## [8] "And finally, number five, we've got to champion small business."
## [9] "Small business is where jobs come from."
## [10] "That's not the kind of small business promotion we need."
## Get Associated Terms
get_terms(ca2, .4)[inds]
## $`11`
## term weight
## 1 yeah 1
##
## $`21`
## term weight
## 1 regulation 1
##
## $`28`
## term weight
## 1 got 1.0000000
## 2 actually 0.5421049
##
## $`68`
## term weight
## 1 bin 1.000000
## 2 laden 1.000000
## 3 osama 0.449873
##
## $`90`
## term weight
## 1 business 1.000000
## 2 small 0.679014
## Pretty Printed Topics
## Get Associated Terms
get_terms(ca2, .4) %>%
as_topic()
## Cluster 2 (n=1409): going, people, said, can, make, one, governor, get...
## Cluster 25 (n=54): need, keep, thought, indict, speak, progress, trying, standard...
## Cluster 15 (n=50): want, thirty, now, leave, bigger
## Cluster 39 (n=46): jobs, investing
## Cluster 61 (n=39): education, doubt, oil, lands, public
## Cluster 36 (n=37): thousand, hundred, eighty, two
## Cluster 40 (n=33): middle, class, east, certainly
## Cluster 17 (n=31): israel, part, experience, united, way, states
## Cluster 31 (n=29): years, four, last
## Cluster 37 (n=28): tax, deductions, amount
## Cluster 27 (n=25): military, maintaining, spending
## Cluster 46 (n=23): important, gone, think, mistake, tough
## Cluster 62 (n=23): thank, gentlemen
## Cluster 10 (n=22): talk, two, minute, minutes, toss
## Cluster 14 (n=21): back, medicare, come, manufacturing
## Cluster 16 (n=21): right
## Cluster 22 (n=21): example, chance, give, state, let
## Cluster 55 (n=21): mister, president
## Cluster 30 (n=20): happened, exactly
## Cluster 65 (n=20): governor
## Cluster 81 (n=20): china, problem, compete
## Cluster 19 (n=19): economy, grows
## Cluster 35 (n=19): deal, trade
## Cluster 42 (n=19): percent, seven
## Cluster 44 (n=19): trillion, dollar
## Cluster 84 (n=19): first, year
## Cluster 1 (n=18): care, health
## Cluster 24 (n=18): get, jeremy, rid
## Cluster 28 (n=18): got, actually
## Cluster 54 (n=18): role, leadership, government, kind, shown
## Cluster 70 (n=18): bush, different
## Cluster 26 (n=17): respond, will, lose
## Cluster 32 (n=17): future, bright, critical
## Cluster 76 (n=17): energy
## Cluster 34 (n=16): sure, make, job, college
## Cluster 43 (n=16): taxes, cut
## Cluster 13 (n=15): please, ask, repealed, quickly
## Cluster 67 (n=15): war, end, iraq
## Cluster 4 (n=14): one, number
## Cluster 63 (n=14): grow, planning
## Cluster 79 (n=14): coal
## Cluster 23 (n=13): dodd, frank, repeal
## Cluster 38 (n=13): three, twenty, million
## Cluster 56 (n=13): question
## Cluster 78 (n=13): true
## Cluster 96 (n=13): iran, bomb, closer, nuclear
## Cluster 21 (n=12): regulation
## Cluster 47 (n=12): let
## Cluster 51 (n=12): stand, principles
## Cluster 69 (n=12): election, course
## Cluster 72 (n=12): thank
## Cluster 6 (n=11): happen
## Cluster 57 (n=11): difference
## Cluster 59 (n=11): happy, teachers
## Cluster 74 (n=11): know
## Cluster 89 (n=11): balanced, budget
## Cluster 90 (n=11): business, small
## Cluster 33 (n=10): romney, governor
## Cluster 45 (n=10): plan
## Cluster 75 (n=10): detroit, bankrupt
## Cluster 77 (n=10): policies
## Cluster 83 (n=10): still, speaking
## Cluster 95 (n=10): policy, failure, foreign
## Cluster 98 (n=10): sanctions, tighten, crippling
## Cluster 7 (n=9): private
## Cluster 8 (n=9): high
## Cluster 66 (n=9): done
## Cluster 82 (n=9): answer, straightforward
## Cluster 92 (n=9): said
## Cluster 100 (n=9): strong
## Cluster 3 (n=8): billion, dollar, ninety, sixteen
## Cluster 18 (n=8): absolutely
## Cluster 41 (n=8): tell
## Cluster 50 (n=8): move, along
## Cluster 73 (n=8): good, night
## Cluster 80 (n=8): production
## Cluster 86 (n=8): create, jobs
## Cluster 5 (n=7): choice
## Cluster 9 (n=7): point, last, make
## Cluster 49 (n=7): wrong
## Cluster 53 (n=7): see
## Cluster 60 (n=7): stamps, food, million
## Cluster 64 (n=7): excuse, sir
## Cluster 68 (n=7): bin, laden, osama
## Cluster 71 (n=7): record, check
## Cluster 97 (n=7): bob
## Cluster 29 (n=6): believe
## Cluster 85 (n=6): candy
## Cluster 91 (n=6): understand
## Cluster 48 (n=5): well
## Cluster 58 (n=5): great
## Cluster 87 (n=5): thanks
## Cluster 88 (n=5): yes
## Cluster 93 (n=5): lorraine
## Cluster 94 (n=5): pension, looked
## Cluster 11 (n=4): yeah
## Cluster 12 (n=4): sorry
## Cluster 20 (n=4): much, cut
## Cluster 52 (n=4): time
## Cluster 99 (n=4): work
It seems to me that if the hierarchical clustering is function as expected we'd see topics clustering together within a conversation as the natural eb and flow of a conversation is to talk around a topic for a while and then move on to the next related topic. A Gantt style plot of topics across time seems like an excellent way to observe clustering across time. In the experiment I first ran the hierarchical clustering at the sentence level for all participants in the 2012 presidential debates data set. I then decided to use turn of talk as the unit of analysis. Finally, I pulled out the two candidates (President Obama and Romney) and faceted n their topic use over time.
if (!require("pacman")) install.packages("pacman")
pacman::p_load(dplyr, clustext, textshape, ggplot2, stringi)
myfit3 <- presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
with(data_store(dialogue)) %>%
hierarchical_cluster()
plot(myfit3, 75)
Can & Ozkarahan's (1990) formula indicated a k = 259. This umber
seemed overly large. I used k = 75 for the number of topics as it
seemed unreasonable that there'd be more topics than this but with
k = 75 over half of the sentences loaded on one cluster. Note the use
of the attribute join from assign_cluster to make joining back to
the original data set easier.
k <- 75
ca3 <- assign_cluster(myfit3, k = k)
presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
tbl_df() %>%
attributes(ca3)$join() %>%
group_by(time) %>%
mutate(
word_count = stringi::stri_count_words(dialogue),
start = starts(word_count),
end = ends(word_count)
) %>%
na.omit() %>%
mutate(cluster = factor(cluster, levels = k:1)) %>%
ggplot2::ggplot(ggplot2::aes(x = start-2, y = cluster, xend = end+2, yend = cluster)) +
ggplot2::geom_segment(ggplot2::aes(position="dodge"), color = 'white', size = 3) +
ggplot2::theme_bw() +
ggplot2::theme(panel.background = ggplot2::element_rect(fill = 'grey20'),
panel.grid.minor.x = ggplot2::element_blank(),
panel.grid.major.x = ggplot2::element_blank(),
panel.grid.minor.y = ggplot2::element_blank(),
panel.grid.major.y = ggplot2::element_line(color = 'grey35'),
strip.text.y = ggplot2::element_text(angle=0, hjust = 0),
strip.background = ggplot2::element_blank()) +
ggplot2::facet_wrap(~time, scales='free', ncol=1) +
ggplot2::labs(x="Duration (words)", y="Cluster")
## Warning: Ignoring unknown aesthetics: position
Right away we notice that not all topics are used across all three
times. This is encouraging that the clustering is working as expected as
we'd expect some overlap in debate topics as well as some unique topics.
However, there were so many topics clustering on cluster 3 that I had to
make some decisions. I could (a) ignore this mass and essentially throw
out half the data that loaded on a single cluster, (b) increase k to
split up the mass loading on cluster 3, (c) change the unit of analysis.
It seemed the first option was wasteful of data and could miss
information. The second approach could lead to a model that had so many
topics it wouldn't be meaningful. The last approach seemed reasonable,
inspecting the cluster text showed that many were capturing functions of
language rather than content. For example, people use "Oh." to
indicate agreement. This isn't a topic but the clustering would group
sentences that use this convention together. Combining this sentence
with other sentences in the turn of talk are more likely to get the
content we're after.
Next I used the textshape::combine function to group turns of talk
together.
myfit4 <- presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
textshape::combine() %>%
with(data_store(dialogue, stopwords = tm::stopwords("english"), min.char = 3)) %>%
hierarchical_cluster()
plot(myfit4, k = 80)
The distribution of turns of talk looked much more dispersed across
clusters. I used k = 60 for the number of topics.
k <- 80
ca4 <- assign_cluster(myfit4, k = k)
presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
textshape::combine() %>%
tbl_df() %>%
attributes(ca4)$join() %>%
group_by(time) %>%
mutate(
word_count = stringi::stri_count_words(dialogue),
start = starts(word_count),
end = ends(word_count)
) %>%
na.omit() %>%
mutate(cluster = factor(cluster, levels = k:1)) %>%
ggplot2::ggplot(ggplot2::aes(x = start-2, y = cluster, xend = end+2, yend = cluster)) +
ggplot2::geom_segment(ggplot2::aes(position="dodge"), color = 'white', size = 3) +
ggplot2::theme_bw() +
ggplot2::theme(panel.background = ggplot2::element_rect(fill = 'grey20'),
panel.grid.minor.x = ggplot2::element_blank(),
panel.grid.major.x = ggplot2::element_blank(),
panel.grid.minor.y = ggplot2::element_blank(),
panel.grid.major.y = ggplot2::element_line(color = 'grey35'),
strip.text.y = ggplot2::element_text(angle=0, hjust = 0),
strip.background = ggplot2::element_blank()) +
ggplot2::facet_wrap(~time, scales='free', ncol=1) +
ggplot2::labs(x="Duration (words)", y="Cluster")
## Warning: Ignoring unknown aesthetics: position
The plots looked less messy and indeed topics do appear to be clustering around one another. I wanted to see how the primary participants, the candidates, compared to each other in topic use.
In this last bit of analysis I filter out all participants except Obama and Romeny and facet by participant across time.
myfit5 <- presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
textshape::combine() %>%
filter(person %in% c("ROMNEY", "OBAMA")) %>%
with(data_store(dialogue, stopwords = tm::stopwords("english"), min.char = 3)) %>%
hierarchical_cluster()
plot(myfit5, 50)
Based on the dendrogram, I used k = 50 for the number of topics.
k <- 50
ca5 <- assign_cluster(myfit5, k = k)
presidential_debates_2012 %>%
mutate(tot = gsub("\\..+$", "", tot)) %>%
textshape::combine() %>%
filter(person %in% c("ROMNEY", "OBAMA")) %>%
tbl_df() %>%
attributes(ca5)$join() %>%
group_by(time) %>%
mutate(
word_count = stringi::stri_count_words(dialogue),
start = starts(word_count),
end = ends(word_count)
) %>%
na.omit() %>%
mutate(cluster = factor(cluster, levels = k:1)) %>%
ggplot2::ggplot(ggplot2::aes(x = start-10, y = cluster, xend = end+10, yend = cluster)) +
ggplot2::geom_segment(ggplot2::aes(position="dodge"), color = 'white', size = 3) +
ggplot2::theme_bw() +
ggplot2::theme(panel.background = ggplot2::element_rect(fill = 'grey20'),
panel.grid.minor.x = ggplot2::element_blank(),
panel.grid.major.x = ggplot2::element_blank(),
panel.grid.minor.y = ggplot2::element_blank(),
panel.grid.major.y = ggplot2::element_line(color = 'grey35'),
strip.text.y = ggplot2::element_text(angle=0, hjust = 0),
strip.background = ggplot2::element_blank()) +
ggplot2::facet_grid(person~time, scales='free', space='free') +
ggplot2::labs(x="Duration (words)", y="Cluster")
## Warning: Ignoring unknown aesthetics: position
If you're curious about the heaviest weighted tf-idf terms in each cluster the next code chunk provides the top five weighted terms used in each cluster. Below this I provide a bar plot of the frequencies of clusters to help put the other information into perspective.
invisible(Map(function(x, y){
if (is.null(x)) {
cat(sprintf("Cluster %s: ...\n", y))
} else {
m <- dplyr::top_n(x, 5, n)
o <- paste(paste0(m[[1]], " (", round(m[[2]], 1), ")"), collapse="; ")
cat(sprintf("Cluster %s: %s\n", y, o))
}
}, get_terms(ca5, .4), names(get_terms(ca5, .4))))
## Cluster 1: going (1); time (0.6); get (0.5); years (0.5); like (0.4)
## Cluster 2: trillion (1); dollar (0.9); billion (0.5)
## Cluster 3: one (1); number (0.9)
## Cluster 4: get (1); private (0.7); medicare (0.5)
## Cluster 5: election (1); choice (0.9)
## Cluster 6: two (1); eighty (0.9); thousand (0.6); dollar (0.5); hundred (0.4)
## Cluster 7: happen (1)
## Cluster 8: care (1); government (0.9); keep (0.7); federal (0.6); health (0.5)
## Cluster 9: war (1); high (0.9); end (0.8); iraq (0.5)
## Cluster 10: good (1); forward (0.6); know (0.6)
## Cluster 11: make (1); sure (0.9); point (0.7); want (0.6); last (0.5)
## Cluster 12: sorry (1); china (0.9); record (0.7); talk (0.6); problem (0.5)
## Cluster 13: absolutely (1)
## Cluster 14: yes (1); places (0.5)
## Cluster 15: let (1); respond (0.7); tell (0.7); bob (0.7); example (0.5)
## Cluster 16: dodd (1); frank (1)
## Cluster 17: cut (1); taxes (0.8)
## Cluster 18: believe (1)
## Cluster 19: three (1)
## Cluster 20: jobs (1)
## Cluster 21: middle (1); class (0.6); east (0.5); certainly (0.5)
## Cluster 22: plan (1)
## Cluster 23: well (1); first (0.7); year (0.6); posture (0.6)
## Cluster 24: wrong (1)
## Cluster 25: great (1); bush (0.7); different (0.6); teachers (0.6)
## Cluster 26: difference (1)
## Cluster 27: military (1)
## Cluster 28: stamps (1); food (1); million (0.4)
## Cluster 29: job (1); college (0.8); find (0.6)
## Cluster 30: pension (1); mister (0.9); speaking (0.6); still (0.5); looked (0.5)
## Cluster 31: business (1); grow (0.8); small (0.8); planning (0.5)
## Cluster 32: done (1)
## Cluster 33: thank (1)
## Cluster 34: four (1); last (1); years (0.9)
## Cluster 35: question (1); answer (0.8); straightforward (0.5)
## Cluster 36: detroit (1); bankrupt (0.5)
## Cluster 37: energy (1)
## Cluster 38: percent (1); seven (0.5)
## Cluster 39: right (1); course (0.6)
## Cluster 40: governor (1)
## Cluster 41: production (1); coal (0.9); oil (0.5); gas (0.4)
## Cluster 42: true (1)
## Cluster 43: candy (1)
## Cluster 44: economy (1); grows (0.5)
## Cluster 45: balanced (1); budget (0.9)
## Cluster 46: leadership (1); kind (0.8); role (0.5); shown (0.5); show (0.5)
## Cluster 47: said (1)
## Cluster 48: iran (1); nuclear (0.5)
## Cluster 49: work (1)
## Cluster 50: strong (1)
invisible(summary(ca5))
It appears that in fact the topics do cluster within segments of time as we'd expect. This is more apparent when turn of talk is used as the unit of analysis (document level) rather than each sentence.