A spider chart is a graphical method of displaying multivariate data in the form of a two-dimensional chart of three or more quantitative variables represented on axes starting from the same point. The relative position and angle of the axes is typically uninformative.
It consists of a sequence of equi-angular spokes, called radii, with each spoke representing one of the variables. The data length of a spoke is proportional to the magnitude of the variable for the data point relative to the maximum magnitude of the variable across all data points.
A line is drawn connecting the data values for each spoke. This gives the plot a star-like appearance and the origin of the name of this plot.
Spider charts are useful when you want to look at several different factors all related to one item. spider charts have multiple axes along which data can be plotted
Application
The "spider chart" can be a format commonly used by management consultants to show their clients how an organization compares with those in similar companies.
It also can be used as the control of quality improvement to display the performance metrics of any ongoing program.
Furthermore, it is also being used in sports to chart players' strengths and weaknesses.
For example, you could use a spider chart to compile data about a wide receiver on a professional football team. On one axis, you could plot the percentage of passes caught.
Another axis would show his yards per completion; another, his completions per 100 plays; another, blocks made; and a final axis might show his interceptions
So far as we can see, the spider has a broad application area.
Comparison with radar chart in dojox.charting
Spider charts differ from radar chart in that a spider chart is a chart that has N "y" axes while radar chart has only one "y" axis, all radiating from a central point,
where each "y" axis represents a specific category. For example, there are 5 "y" axes: GDP, area, population, inflation and growth here.
The radar chart, however, instead of being drawn in a typical linear X/Y space, the radar chart is drawn using a circular plot, with specific X values being shown using an arbitrary number of spokes drawn from a center point.
These charts are useful for showing data over a cyclical set of values (for instance, hours of a day, minutes in an hour, etc.). With a radar chart, data is plotted in much the same way as with a typical line or area chart.
Actually, the radar chart is somewhat similar with line chart, the major difference between them is: line chart has a "straight" X axis while radar chart has a "circular" X axis, and the orientation of their Y axis is opposite.