Visualization of Similar Features - Correlations

In general, the procedure used for visualization of the similarity between features, or for correlation of the features, is the same as that used for visualization of the similarity between objects. If one transposes the matrix of objects and features, the same methods may be used. It is, however, easier to imagine correlating features which describe the similarity of the functional shapes of variables and the similarity of objects, e.g. the similarity of different samples, than the other way around. 

For this reason we deal with the visualization of relationships between the features. For three features only, there are many possibilities for graphical representation  

But for most cases of interest in the field of environmental research there are more than three features. 

In general, the matrix scatter plot is the direct graphical representation of the correlation matrix (see Section 5.4). Fig. 5-5 also demonstrates the histogram of the single features in the main diagonal as additional information. 

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