In jsphdms/runchart: Run Charts with Automatic Rebasing

Introduction

A run chart is a simple analytical tool that helps us understand changes in data over time. - NHS Healthcare Improvement Scotland.

Run charts^[As defined by the NHS Scotland Quality Improvement Hub] are non-trivial to automate. A number of solutions exist in the healthcare improvement community in Scotland. However the author is only aware of small-scale solutions such as scripts and Excel macros.

These kinds of approaches have the following limitations:

Version control is cumbersome and unrealistic.
Adding a separate script to an existing workflow is inconvenient and error prone.
Scripts are often written to operate under specific conditions; making wider adoption unlikely.
Testing edge cases is a time consuming task which is replicated with each new script or macro.

The runchart package aims to overcome these limitations by exporting a single, well tested, function of the same name: runchart().

Getting Started

Install the package using like this:

# install.packages("devtools")
devtools::install_github('jsphdms/runchart')

For example:

Code for plotting the result might look like this:

Things to Notice

There are several behaviours to notice in the plot above:

Rephasing for each sustained shift (9 consecutive points all above/below the baseline).
Shifts are identified (6 or more consecutive points all above/below the baseline).
Missing values are ignored. For example the 27th data point above is missing, which causes the rephased baseline to be longer than the first.
Non-useful observations are ignored. For example the 15th data point above lands exactly on the first baseline. Therefore it neither breaks nor contributes to the observed shift.