Radar Chart
A Radar Chart, sometimes referred to as a Spider Chart or Star Chart, is a circular graph used primarily as a data comparison tool. These charts normally have a circular shape, but can also be displayed as a polygon. The Radar chart is a very effective tool for comparing multiple entities based on different characteristics. For instance, they can be used for comparing various laptops based on their processor, graphic cards, memory, storage, etc.

Unlike most other chart types, the Radar chart does not plot an X value. Radar Chart X values are ignored for all Radar chart series. Instead, radar chart 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.

So basically a radar chart graphically shows the size of the gaps among five to ten organizational performance areas. The chart displays the important categories of performance and makes visible concentrations of strengths and weaknesses.


Application of Radar Charts

• 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.
• Further, radar charts are visually striking, and can add interest to what would otherwise be a dry data presentation.

How to use it:

• Create categories: Headers from an affinity diagram or major parameters to be judged are to be plotted. A radar chart can normally include five to ten parameters.
• Standardize performance definitions: Use standardized definitions of both full performance and non-performance in each category so that ratings are performed consistently. Define the scoring range (e.g., 0 to 5 with 5 being full performance).
• Rate each performance category: Each category is to be rated individually, and then an average or consensus score for each category is developed. Alternatively, an average or consensus score for each category may be developed initially.

Construct the chart.

1. Draw a large circle and insert as many spokes or radii as there are performance categories.
2. Around the perimeter of the circle, label each spoke with the title of a performance category.
3. Subdivide each spoke into the number of increments established in the rating scale.
4. Label the center of the circle where spokes join as 0 (no performance) and place the highest rating number (full or exceptional performance) at the end of the spoke at the outer ring.

Ploting the ratings.

For each performance category, plot on the chart the associated rating. Then connect the plotted points on all the spokes. Highlight the enclosed central shape as necessary for ease in viewing.

Interpret the Radar Charts and using the results.

The resulting radar chart will graphically show areas of relative strength and relative weakness, as well as depicting general overall performance



Limitations of Radar Charts

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.

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
 

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. 

 

Sample of a Radar Chart