Author Archives: norbert

About norbert

Biometrician at Clinical Trial Centre, Leipzig University (GER), with degrees in sociology (MA) and public health (MPH).

How to order factors by level frequency and level name

Intro Quite frequently, factor variables are ordered by level frequency. However, factor levels having only a few observations are sometimes collapsed into one level usually named “others”. Since this level is usually not of particular interest, it may be a … Continue reading

Posted in Tips & Tricks, Visualizing Data | Tagged | 2 Comments

Postleitzahlen mit führender Null richtig formatieren

Intro Importiert man Postleitzahlen aus anderen Datenformaten (z.B. Excel, Access) in R, ist es nicht selten, dass Postleitzahlen programmintern tatsächlich auch als Zahlen abgespeichert werden. Wie ein Blick auf einen im Internet frei verfügbaren Datensatz zeigt, kann dies zu folgendem … Continue reading

Posted in Tips & Tricks | Tagged , | 2 Comments

Scoring the PHQ-9 Questionnaire Using R

Intro The PHQ-9 is the nine-item depression module of the Patient Health Questionnaire. Each of the items is scored on a 4-point Likert scale ranging from 0 (not at all) to 3 (nearly every day). The items are summed to … Continue reading

Posted in Indroduction | Tagged , | Leave a comment

Sample Size Calculation Using R

Preample “Sample Size Calculation Using R” – the title of this blog post – sounds very comprehensive. However, this post only deals with the sample size collection for one particular test (two sample t-test). A collection of functions for basic … Continue reading

Posted in Indroduction | Tagged , , , | Leave a comment

How to Plot Venn Diagrams Using R, ggplot2 and ggforce

Intro Venn diagrams – named after the English logician and philosopher John Venn – “illustrate the logical relationships between two or more sets of items” with overlapping circles. In this tutorial, I'll show how to plot a three set venn … Continue reading

Posted in Visualizing Data | Tagged , | Leave a comment

How to plot GPS data using R, ggplot2 and ggmap

Intro A couple of months ago, I bought a mobile GPS navigation device. The device makes it possible to record the routes we travel with our car. Since the routes can by exported as .gpx files, it is rather easy … Continue reading

Posted in Visualizing Data | Tagged , | Leave a comment

R Markdown: How to place two tables side by side using ‘knitr’ and ‘kableExtra’

Intro When I was recently writing some report using R Markdown, I wanted to place two rather small tables side by side. Since I usually use the kable()-function of the knitr package and the kableExtra package to print tables, I … Continue reading

Posted in Tips & Tricks | Tagged , | 3 Comments