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TreeMap

TreeMaps visually display a hierarchical structure by dividing a rectangular area in proportion to the values of the tree nodes. TreeMaps were invented by Ben Shneiderman in 1990. By now there are various tools and industrial applications of this concept.

This demonstration uses a splice and dice algorithm with a split parameter determining when to switch reducing the x- or the y-axis of the remaining rectangular area. The tree here has 4 branching levels (slider controls how many are visible) and consists of 6 randomly generated values at each node.

There are four controls in this TreeMap demonstration:

Tree Level - use the slider to display trees with levels 1, 2, 3, or 4

Split Ratio - use the slider to change from 0.1 to 0.9; notice impact on treemap layout

Rectangle Shape - drag Locator on top right to change the shape of the bounding rectangle

Color Scheme - chose from pull-down menu of seven built-in color schemes

Use the loop animation on the split ratio (with slower speed for level 3 and 4 trees) to observe the change of split level on the treemap layout. The split ratio determines how the current rectangle container will be divided for all its elements. The cut always happens on the longer dimension (x or y). The ratio determines how many elements at a node level will be included into the part split off from the current rectangle. If you have N elements at one level, then the first k elements will be grouped into the first split of the rectangle if Sum(i=1, k) Elt(i) / Sum(i=1,N) Elt(i) >= ratio.