This is a Shiny application that enables power calculations for pre-trends tests and visualization of possible violations of parallel trends. Calculations are based on Roth (2020). All input to the app is provided in CSV files, which facilitates interaction with many different programming languages (R, Stata, Python, etc.). See also the associated R package, which has detailed documentation.
There are two ways to use the Shiny app.
First, the application can be run locally in RStudio with the following commands
#install.packages("shiny") #install Shiny if not installed
library(shiny)
shiny::runGitHub("PretrendsPower", "jonathandroth")
Second, there is an online version of the app. Unfortunately, the free version of shinyapps limits total usage to 25 hours a month.
Below is a screenshot of the user-interface of the app, which also provides detailed use instructions.