How do I construct a dendrogram (tree diagram) from the output of TWINSPAN?
A. It is possible to construct a dendrogram from the pattern of zeros and ones in the margins of the TWINSPAN table. See the example in McCune and Grace (2002). The pattern or zeros and ones carries information on the series of divisions performed by TWINSPAN. Observe the right-hand side of the table first. The first column of zeros and ones shows the first division — rows receiving a zero were separated from rows receiving ones. Rows receiving the same digit are more similar to each other than rows in different groups. Moving to the right, the next column shows the next two divisions. Each of the preceding groups is again divided, as shown by the pattern of zeros and ones. You can continue these sequential divisions until you reach the rightmost columns — these groups were too small to divide further. You can sketch in a traditional dendrogram to the right of the TWINSPAN table. But it differs a little from the dendrogram you would get by cluster analysis, because in TWINSPAN the fi
