An Alternative Analysis of Two Circular Variables via Graphical Representation

The relationship between variables is vital in data analysis. The scatter plot, for instance, gives an easy preliminary exploratory analysis for finding relationship between two variables, if any. Statistical method such as correlation and linear relationship are standard tools in most statistical packages. For circular variables that take value on the circumference of a circle, the analysis however is different from those of the Euclidean type variables because circumference is a bounded closed space. Unlike linear variable, standard statistical packages for circular variables are limited. This paper proposes a graphical representation of two circular variables as a preliminary analysis using the MATLAB environment. A plot called Spoke plot is developed to visually display relationship between two circular variables and linear correlation. As an illustration, the Malaysian wind data is used in the analysis. This new type of representation promises an alternative approach in the preliminary analysis of circular data.