Text Mining and Visualization

168 Text Mining and Visualization: Case Studies Using Open-Source Tools

iteration. To do this, simply repeat Step 2 nine times, selecting XMeans in Step 2.3 and

varying k from 2 to 10 on each iteration. When we plot the output as a chart, we see a

function similar to that shown in Figure 7.15.

FIGURE 7.15: Sum of squared errors by k for 100,000 filtered sessions from AOL.

As we can see, there is an elbow around k = 4 and another around k = 7. This implies

that either of these two values may be good choices for a local optimum. We have already

seen the output for k = 7 (which is the optimum that XMeans found), so now we repeat

Step 2 with kMeans and