Systematic mapping assesses how much evidence exists on a particular topic – the evidence base. Perhaps the most useful outputs of a systematic map are an interactive database of studies and their metadata, along with visualizations of this database. Despite the rapid increase in systematic mapping as an evidence synthesis method, there is currently a lack of open source software for producing interactive visualizations of systematic map databases. In April 2018, the authors coordinated the first ever Evidence Synthesis Hackathon in Stockholm, and decided to address the lack of software by developing an R-based tool called EviAtlas, an Open Access (i.e. free to use) and Open Source (i.e. software code is freely accessible and reproducible) tool for producing interactive, attractive tables and figures that summarize the evidence base.
This paper presents the new tool, which has the capacity to generate visualizations for systematic maps and reviews, inlcuding: a complete data table; a spatially explicit geographical information system (Evidence Atlas); heat maps that cross-tabulate two or more variables and display the number of studies belonging to multiple categories; and standard descriptive plots showing the nature of the evidence base, for example the number of studies published per year or number of studies per country.
We believe that EviAtlas will provide a stimulus for the development of other innovative tools to facilitate evidence synthesis.