Spider Graph

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 value of each aspect is depicted by the node (anchor) on the spoke (axis) and a  line is drawn connecting the data values for each spoke. Also called a Spider Chart, Radial Chart or Web Chart, Radar Chart help in showing all your data values at one go.

Quick details

What: Discover Rank

Why: Ideal for displaying and comparing multivariate performance

History of Spider Graph

The star plot was first used by Georg von Mayr in 1877. Radar charts differ from glyph plots due to a difference that all variables are used to construct the plotted star figure. There is no separation into foreground and background variables. Instead, the star-shaped figures are usually arranged in a rectangular array on the page. It is somewhat easier to see patterns in the data if the observations are arranged in some non-arbitrary order.

Example star plot from NASA, with some of the most desirable design results represented in the center

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When to Use a Spider Graph?

1Several items need to be compared with more than 5 metrics of features or characteristics

The distinctive feature about the spider chart is that it can enable a general comparison of all metrics to make a decision. One can judge the cover area and observing the sharp points on the metric lines can give one an overall understanding of the pros and cons of each item. This is enabled by the design of the chart where all axes being arranged radially, with equal distances between each other, have gridlines, that connect from axis-to-axis are used as a guide. Each variable value is plotted along its individual axis and all the variables in a dataset and connected together to form a polygon. The radar chart is more suitable when the exact values aren’t critical for a reader but the overall chart tells some story.

3 trainers are ranked on each of the 5 parameters. The color coding for each trainer helps to visually correlate and contrast the trainers over their diverse aspects

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2When required to compare multiple entities across multiple parameters

Use radar charts to easily compare each category along its own axis and compare overall differences as apparent by the size of each radar. As radar charts are a useful way to display multivariate observations with an arbitrary number of variables, every star which represents a single observation can be compared with the other at a glance.

 

The greater the area the star covers the better is its ranking across multiple parameters.
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3Identifying striking commonality and data outliers 

A radar chart is of use for a quick understanding of differences and commonalities and can help in rapid troubleshooting and generating insights. These excel and are most effective when you are comparing target vs achieved performance. In such a scenario target can be represented as one star in the chart while the actual performance is represented by others. By looking at the gaps in distance between target and actual can help one identify progress and help identify anomalies quickly.

This spider chart represents the allocated budget versus actual spending for a given organization
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Types of Spider Graphs

1. Marked Spider Chart

Very similar to the common radar chart, the only difference it has in the presence of having markers to represent each of the data points. 

2. Filled Spider Chart

This chart is similar to the radar chart with the sole difference of having the entire area of the radar filled with a color to assist in demarcation with the other radars.

 

When Not to Use a Spider Graph?

1Too many variable make it cluttered and harder to understand

Having multiple polygons in one Radar Chart makes it hard to read, confusing and too cluttered. Also, if the polygons are filled in, the top polygon covers all the other polygons underneath it. In the case of too many variables, it creates too many axes, the crowd is too much. Though there are multiple axes that have gridlines connecting them for reference, issues arise when you try to compare values across different axes.

2When a comparison between the lengths of different spokes is important

Do not use radar charts when the accuracy of comparison is of importance to make a decision. Radar Charts are not so good for comparing values across each variable, even with the aid of the spiderweb-like grid guide. Comparing values all on a single straight axis is much easier because radial distances are hard to judge visually, hence bar graphs are considered more popular for comparing.

 

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