The star plot: an alternative display method for multivariate data in the analysis of food and drugs

The star plot (SP) is a method of displaying multivariate data. It can be used to display data with more than two variables. Combined with principal component analysis (PCA), more than two PCs can be displayed in one plane. Different variants of this method are applied to an atomic absorption spectrometry (AAS) data set and to three near infra-red (NIR) spectral data sets. The results show that SP offers an easy way of visualising the multivariate data for food and drugs in a plane, and it is able to help the analyst to identify and to detect different qualities of food and drug composition. Moreover, when an object is added or removed, the PC's must be computed all over again, which is not the case for the SP-plot. The application of SP to the examples presented in the text suggests that the SP approach can be applied as an alternative method for displaying multivariate chemometric data in place of PCA or, to improve visualisation of the results already obtained with PCA.