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Last Updated: Oct 30, 2013

Cirrus is a visualization tool that displays a word cloud relating to the frequency of words appearing in one or more documents. One can click on any word appearing in the cloud to obtain detailed information about its relativity.

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DocumentationAttributesUser Supplied Tags
Created: May 26, 2011
Last Updated: Oct 30, 2013
Background processing Not applicable
Ease of use Very easy
Tool family Voyant
Type of analysis Visualization
Type of license Free
Usage New
Web usable Run in browser
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February 08, 2012 06:40 AM

Cirrus Overview

Cirrus is a freely available visualization tool that generates a word cloud from a document or group of documents. The initial word cloud contains all of the most frequent words from the text, laid out graphically to fit together within an elliptical shape. Words may be oriented either vertically or horizontally, and they are rendered in different colours for ease of viewing. The user should be aware that word orientation and colour are strictly decorative elements, they do not indicate anything meaningful about the word. The size of the word, however, indicates the frequency with which it appears in the document. The larger the font size, the more frequent the word. The user can mouse over a word to see the precise number of times that it appears in the document.

Applying Stop Words

One of the problems with word frequency visualization is the prevalence of conjunctions and articles in most texts. These less semantically interesting words often drown out the adjectives, adverbs, nouns, and verbs that are more likely to be of interest to the researcher. Cirrus offers an easy solution to this problem. By clicking the options icon in the upper right hand menu, a user can apply a list of stop words to the visualization. These stop words will be treated as noise, and stripped from the cloud, allowing words of greater interest to surface. Cirrus offers two pre-built lists of stop words, one for common English words, and one for common French words. The user can view the lists, so she know which words will  be removed before applying them.


Cirrus offers users the ability to search within a word cloud for specific words, which is especially useful for seeing all of the word variations in a text. If I enter “comput” in the search box, Cirrus returns a word cloud indicating the word frequency of related terms like computers, computational, computing, computer-generated, computer-literate, microcomputers, human-computer, and supercomputing. It is also possible to enter comma separated terms in the search box in order to compare the frequency of multiple terms. By entering “comput, digit” for example, the user sees all of the variations of computer, as well as digital, digitization, etc. in the resulting word cloud. Any number of terms can be compared in this way.

The Cirrus export menu exposes several options for sharing a word cloud. A permanent URL can be generated for a particular visualization, but the software also provides code snippets that allow the word cloud to be embedded in a website as a button or as a full visualization.

Cirrus vs. Wordle

There are a number of word cloud tools available freely on the internet, but Cirrus is built primarily for academic research, and thus distinguishes itself from popular tools like Wordle in several ways. Wordle allows the user a great deal of control over the look and feel of his word cloud, including options to choose font sets, colour palettes, and backgrounds. Cirrus does not offer user control over these graphic elements. Wordle, however, advertises itself as a “toy”, whereas Cirrus is an academic tool.  In Wordle a user has no control over stop words that are applied to her text, multiple files or copora cannot be uploaded for analysis, and a user cannot perform searches against his text to visualize word stems and variations, or to compare multiple terms of interest.

Finally, it must be mentioned that, as part of the Voyant workbench, Cirrus is integrated into a large and powerful set of text analysis tools that allow extremely granular manipulation of text corpora. Clicking on any word in the Cirrus word cloud will expose that text in a suite of other analysis tools that allow further investigation of the document or corpus. It is beyond the scope of this review to describe the full suite of Voyant tools, but a comprehensive list is available here: http://hermeneuti.ca/voyeur/tools.

Suggestions for Improvement

As I played with the tool I had a couple of suggestions for improvement. The stop word feature would be more useful if the end-user were permitted to customize an instance of the list with his or her own specific terms. I also wished for an export option that would allow me to download an excel spreadsheet containing a list of all unique words in the document with a separate column for the word count beside each. Ideally this list would also exclude stop words if they had been excluded in my cloud.

Cirrus is a useful tool for initial exploration of a text. It allows a researcher to quickly pinpoint major themes, to visually explore word variations, and to compare the frequencies of terms that are of particular interest. It can process large corpora with impressive speed, and exposes many options for document input. Cirrus is a tool for the serious researcher who is more interested in the content of her text than the colours in her word cloud. 

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