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182 Part II • Descriptive Analytics

gAntt ChARt Gantt charts are a special case of horizontal bar charts that are used to
portray project timelines, project tasks/activity durations, and overlap amongst the tasks/
activities. By showing start and end dates/times of tasks/activities and the overlapping
relationships, Gantt charts make an invaluable aid for management and control of
projects. For instance, Gantt charts are often used to show project timeline, talk overlaps,
relative task completions (a partial bar illustrating the completion percentage inside a
bar that shows the actual task duration), resources assigned to each task, milestones,
and deliverables.

peRt ChARt PERT charts (also called network diagrams) are developed primarily
to simplify the planning and scheduling of large and complex projects. A PERT chart
shows precedence relationships among the project activities/tasks. It is composed
of nodes (represented as circles or rectangles) and edges (represented with directed
arrows). Based on the selected PERT chart convention, either nodes or the edges may
be used to represent the project activities/tasks (activity-on-node versus activity-on-arrow
representation schema).

geogRAphiC MAp When the data set includes any kind of location data (e.g., physical
addresses, postal codes, state names or abbreviations, country names, latitude/ longitude,
or some type of custom geographic encoding), it is better and more informative to see
the data on a map. Maps usually are used in conjunction with other charts and graphs,
as opposed to by themselves. For instance, one can use maps to show distribution
of customer service requests by product type (depicted in pie charts) by geographic
locations. Often a large variety of information (e.g., age distribution, income distribution,
education, economic growth, population changes, etc.) can be portrayed in a geographic
map to help decide where to open a new restaurant or a new service station. These types
of systems are often called geographic information systems (GIS).

Bullet Bullet graphs are often used to show progress toward a goal. A bullet graph
is essentially a variation of a bar chart. Often they are used in place of gauges, meters,
and thermometers in dashboards to more intuitively convey the meaning within a much
smaller space. Bullet graphs compare a primary measure (e.g., year-to-date revenue) to
one or more other measures (e.g., annual revenue target) and present this in the context
of defined performance metrics (e.g., sales quota). A bullet graph can intuitively illustrate
how the primary measure is performing against overall goals (e.g., how close a sales
representative is to achieving his/her annual quota).

heAt MAp Heat maps are great visuals to illustrate the comparison of continuous values
across two categories using color. The goal is to help the user quickly see where the
intersection of the categories is strongest and weakest in terms of numerical values of
the measure being analyzed. For instance, heat maps can be used to show segmentation
analysis of the target market where the measure (color gradient would be the purchase
amount) and the dimensions would be age and income distribution.

highlight tABle Highlight tables are intended to take heat maps one step further. In
addition to showing how data intersects by using color, highlight tables add a number
on top to provide additional detail. That is, it is a two-dimensional table with cells
populated with numerical values and gradients of colors. For instance, one can show
sales representative performance by product type and by sales volume.

tRee MAp Tree maps display hierarchical (tree-structured) data as a set of nested
rectangles. Each branch of the tree is given a rectangle, which is then tiled with

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