Object Scores
The following figure shows a plot of the object scores, in which the subjects are labeled with their diagnosis category.
This plot does not help to interpret the first dimension, because patients are not separated by diagnosis along it. However, there is some information about the second dimension. Anorexia subjects (1) and patients with atypical eating disorder (4) form a group, located above subjects with some form of bulimia (2 and 3). Thus, the second dimension separates bulimic patients from others, as you have also seen in the previous section (the variables in the bulimic bundle have large positive component loadings in the second dimension). This makes sense, given that the component loadings of the symptoms that are traditionally associated with bulimia have large values in the second dimension.
This figure shows a plot of the object scores, in which the subjects are labeled with their time of diagnosis.
Labeling the object scores by time reveals that the first dimension has a relation to time because there seems to be a progression of times of diagnosis from the 1’s mostly to the left and others to the right. Note that you can connect the time points in this plot by saving the object scores and creating a scatterplot using the dimension 1 scores on the x axis, the dimension 2 scores on the y axis, and setting the markers using the patient numbers.
Comparing the object scores plot labeled by time with the one labeled by diagnosis can give you some insight into unusual objects. For example, in the plot labeled by time, there is a patient whose diagnosis at time 4 lies to the left of all other points in the plot. This is unusual because the general trend of the points is for the later times to lie further to the right. Interestingly, this point that seems out of place in time also has an unusual diagnosis, in that the patient is an anorectic whose scores place the patient in the bulimic cluster. By looking in the table of object scores, you find that this is patient 43, diagnosed with anorexia nervosa, whose object scores are shown in the following table.
| Time | Dimension 1 | Dimension 2 |
|---|---|---|
| 1 | –2.031 | 1.250 |
| 2 | –2.067 | 0.131 |
| 3 | –1.575 | –1.467 |
| 4 | –2.405 | –1.807 |
The patient’s scores at time 1 are prototypical for anorectics, with the large negative score in dimension 1 corresponding to poor body image and the positive score in dimension 2 corresponding to anorectic symptoms or poor psychosocial behavior. However, unlike the majority of patients, there is little or no progress in dimension 1. In dimension 2, there is apparently some progress toward “normal” (around 0, between anorectic and bulimic behavior), but then the patient shifts to exhibit bulimic symptoms.