@article {10.3389/fphy.2018.00045,
	title = {Rank Dynamics of Word Usage at Multiple Scales},
	journal = {Frontiers in Physics},
	volume = {6},
	year = {2018},
	pages = {45},
	abstract = {The recent dramatic increase in online data availability has allowed researchers to explore human culture with unprecedented detail, such as the growth and diversification of language. In particular, it provides statistical tools to explore whether word use is similar across languages, and if so, whether these generic features appear at different scales of language structure. Here we use the Google Books $N$-grams dataset to analyze the temporal evolution of word usage in several languages. We apply measures proposed recently to study rank dynamics, such as the diversity of $N$-grams in a given rank, the probability that an $N$-gram changes rank between successive time intervals, the rank entropy, and the rank complexity. Using different methods, results show that there are generic properties for different languages at different scales, such as a core of words necessary to minimally understand a language. We also propose a null model to explore the relevance of linguistic structure across multiple scales, concluding that $N$-gram statistics cannot be reduced to word statistics. We expect our results to be useful in improving text prediction algorithms, as well as in shedding light on the large-scale features of language use, beyond linguistic and cultural differences across human populations.},
	issn = {2296-424X},
	doi = {10.3389/fphy.2018.00045},
	url = {https://www.frontiersin.org/article/10.3389/fphy.2018.00045},
	author = {Morales, Jos{\'e} A. and Colman, Ewan and S{\'a}nchez, Sergio and S{\'a}nchez-Puig, Fernanda and Pineda, Carlos and I{\~n}iguez, Gerardo and Cocho, Germinal and Flores, Jorge and Gershenson, Carlos}
}
@article {10.1371/journal.pone.0121898,
	title = {Rank Diversity of Languages: Generic Behavior in Computational Linguistics},
	journal = {PLoS ONE},
	volume = {10},
	number = {4},
	year = {2015},
	month = {04},
	pages = {e0121898},
	publisher = {Public Library of Science},
	abstract = {<p>Statistical studies of languages have focused on the rank-frequency distribution of words. Instead, we introduce here a measure of how word ranks change in time and call this distribution rank diversity. We calculate this diversity for books published in six European languages since 1800, and find that it follows a universal lognormal distribution. Based on the mean and standard deviation associated with the lognormal distribution, we define three different word regimes of languages: {\textquotedblleft}heads{\textquotedblright} consist of words which almost do not change their rank in time, {\textquotedblleft}bodies{\textquotedblright} are words of general use, while {\textquotedblleft}tails{\textquotedblright} are comprised by context-specific words and vary their rank considerably in time. The heads and bodies reflect the size of language cores identified by linguists for basic communication. We propose a Gaussian random walk model which reproduces the rank variation of words in time and thus the diversity. Rank diversity of words can be understood as the result of random variations in rank, where the size of the variation depends on the rank itself. We find that the core size is similar for all languages studied.</p>
},
	doi = {10.1371/journal.pone.0121898},
	url = {http://dx.doi.org/10.1371\%2Fjournal.pone.0121898},
	author = {Cocho, Germinal and Flores, Jorge and Gershenson, Carlos and Pineda, Carlos and S{\'a}nchez, Sergio}
}
