When the Truth Hits You Between the Eyes

Abstract

Visual data analysis is an important first step when evaluating intervention effects. This also holds for analyzing data from single-case experiments. Because most software packages do not offer customized facilities for constructing single-case graphs and are not particularly suited to perform single-case visual data analyses, we created an R package to help researchers in making graphical representations of single-case data and to transform graphical displays back to raw data. In addition to a basic plotting function, we included some tools to facilitate the use of three interpretative principles for visually analyzing single-case data: plotting a measure of central location as a horizontal reference line; displaying variability with (trimmed) range bars, range lines, and trended ranges; and displaying trends with a vertical line graph, by fitting a robust linear trend, or by plotting running medians. Finally, we included a function to extract raw data values from published graphs.