Читать книгу Multiblock Data Fusion in Statistics and Machine Learning - Tormod Næs - Страница 21

When discussing types of data, it is useful to distinguish between direct and indirect data. Direct data are always in the form of a matrix or table containing measurements of variables on a set of samples. Indirect data or derived data are always in the form of variables × variables or samples times samples matrices. Examples of such types of data are cross-products of matrices of direct data, covariances, distances and the like. The main focus in this book is on direct data, but we will discuss some indirect methods as well. First, to limit ourselves and, secondly, analyses on direct data are usually easier to understand and interpret. Thirdly, in many applications of multiblock data analysis in the natural and life sciences, direct data are available. For a more formal description of this distinction, see Section 2.2.1.