Coomans plot

A useful tool in the interpretation of SIMCA is the so-called Coomans plot [32]. It is applied to the discrimination of two classes (Fig. 33.18). The distance from the model for class 1 is plotted against that from model 2. On both axes, one indicates the critical distances. In this way, one defines four zones class 1, class 2, overlap of class 1 and 2 and neither class 1 nor class 2. By plotting objects in this plot, their classification is immediately clear. It is also easy to visualize how certain a classification is. In Fig. 33.18, object a is very clearly within class 1, object b is on the border of that class but is not close to class 2 and object c clearly belongs to neither class. 

Fig. 33.18. The Coomans plot. Object a belongs to class 1, object b is a borderline class 1 object, object c is an outlier towards the two classes.

FIGURE 5.11 The Coomans plot uses the distances of the objects to the PCA models of two groups. It visualizes whether objects belong to one of the groups, to both, or to none. 

Figure 6. Class Distance Plot Coomans Plot). Models are fitted separately to each class (Etu resp. Tellus). The distances for each object to the two classes are plotted. The dashed line indicates equal class distance. The soil samples (object 1-3) are located close to this line.

Distance from the class A model FIGURE 2.13 Example of Coomans plot. 

FIGURE 2.20 Coomans plot of SIMCA models of three-months and six-months aged wine samples (reproduced from Parra et al., 2006a, with permission). 

FIGURE 2.23 Coomans plot of SIMCA models of green teas according to the presence of tannic acid (reproduced from Lvova et ai, 2003, with permission). 

Using the vectors of means for each group, then values for dm and dm2 can be calculated for every sample. A plot of dm against dm2 is referred to as a Coomans plot and displays the results of classification (Figure 10). 

FIGURE 26 SIMCA of oil samples Coomans plot. (Inset) Detail of the portion of the plot corresponding to low values of distance to the model. 

FIGURE 5.4D Cooman s plot that shows the results from SIMCA modeling. Rats treated with chloroquine (fc) and amiodarone (fa) are classified in the phospholipidosis region with only one rat outside the 95% confidence limit. 

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