Radar
Chart:
A radar 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.
The radar chart is also known
as web chart, spider chart, star chart,star plot, cobweb chart, irregular
polygon, polar chart, or kiviat diagram.
Example star plot from NASA, with some of the
most desirable design results represented in the center.
The radar chart is a chart or plot that 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 one of the popular names for this plot. The star plot can be used to
answer the following questions:
- Which observations are most similar, i.e., are there clusters of observations? Radar charts are used to examine the relative values for a single data point
- Are there outliers?
Radar charts are a useful way to display multivariate
observations with an arbitrary number of variables. Each star represents a
single observation. Typically, radar charts are generated in a multi-plot
format with many stars on each page and each star representing one observation.
The star plot was first used by Georg von Mayr in 1877. It is somewhat easier
to see patterns in the data if the observations are arranged in some order i.e.
if the variables are assigned to the rays of the star in some meaningful order.
Radar charts are visually striking, and can add
interest to what would otherwise be a dry data presentation.
Application:
One application of radar charts is the control of
quality improvement to display the performance metrics of any ongoing program.
They are also being used in sports to chart
players' strengths and weaknesses, where they are usually called spider charts.
Radar Charts are frequently used in performance
appraisals to denote targets vs actual performance or in competency based
assessments to denote potential vs actual performance. An example is as below:
Limitations
Radar charts are primarily suited for strikingly
showing outliers and commonality, or when one chart is greater in
every variable than another, and primarily used for ordinal measurements –
where each variable corresponds to "better" in some respect, and all
variables on the same scale.
Conversely, radar charts have been criticized as
poorly suited for making trade-off decisions – when one chart is greater than
another on some variables, but less on others.
Further, it is hard to visually compare lengths
of different spokes, because radial distances are hard to judge, though
concentric circles help as grid lines. Instead, one may use a simple line
graph, particularly for time series.
Radar charts are helpful for
small-to-moderate-sized multivariate data sets. Their primary weakness is that
their effectiveness is limited to data sets with less than a few hundred
points. After that, they tend to be overwhelming.
Submitted By-
Padmini Santi14032
GroupF
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