Scatterplot matrix

Fig. 8.20. Scatterplot matrix of five trace elements in 19 wine samples one of the samples is marked (+) in all the special plots to have the opportunity for comparison (according to Danzer et al. [2001])...

A scatterplot matrix is a well-known technique to show all possible scatterplots of a multidimensional dataset with a relatively small number of dimensions. The statistical package R has a version of scatterplot matrix visualization. The following command will show a scatterplot matrix visualization for the multidimensional dataset in Examples 7.1 and 7.2 using only the first five dimensions. The scatterplot matrix in Figure 7.3 shows univariate displays down the diagonal and each nondiagonal cell shows a scatterplot for the two corresponding dimensions. 

Figure 7.3 Scatterplot matrix visualization for first five dimensions of multidimensional dataset with 33 muscular dystrophy samples and 878 genes. (See color insert.)...

Michael Friendly s Corrgram (Friendly, 2002) uses a color- and shape-coded scatterplot matrix display (Tukey and Tukey, 1981) to show correlations between variables. Variables are permuted so that correlated variables are positioned adja-centiy. Guo (2003) and Guo et al. (2003) also evaluated all possible axis-parallel 2D projections according to the maximum conditional entropy to identify ones that are most useful to find clusters. They visualized the entropy values in a matrix display called the entropy matrix (MacEachren et al., 2003) that is also a color-coded scatterplot matrix. 

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