Recent studies have shown that macroscopic patterns of continuity and change
over the course of centuries can be detected through the analysis of time
series extracted from massive textual corpora. Similar data-driven approaches
have already revolutionised the natural sciences, and are widely believed to
hold similar potential for the humanities and social sciences, driven by the
mass-digitisation projects that are currently under way, and coupled with the
ever-increasing number of documents which are "born digital". As such, new
interactive tools are required to discover and extract macroscopic patterns
from these vast quantities of textual data. Here we present History Playground,
an interactive web-based tool for discovering trends in massive textual
corpora. The tool makes use of scalable algorithms to first extract trends from
textual corpora, before making them available for real-time search and
discovery, presenting users with an interface to explore the data. Included in
the tool are algorithms for standardization, regression, change-point detection
in the relative frequencies of ngrams, multi-term indices and comparison of
trends across different corpora
