Radar

Radar charts¶

A radar chart (sometimes called a Spider chart or a web chart) is a kind of polar chart that does not use explicit angular value to indicate the location of data points.
Instead, radar charts use a categorical variable that is uniformly projected along the angular axis. A data point is represented using its radial value (usually the quantity or magnitude) and the angle associated with the category of the second variable.

Just like for polar charts, radar charts must have the type property of the chart control set to "scatterpolar".
The r and theta properties are still used to indicate the data sets but here, theta is set to the value of a category. The radar chart automatically arranges all categories along the angular axis.

Key properties¶

Name	Value	Notes
type	`scatterpolar`
r	radial values
theta	angular values	As categorical values.
options	dictionary	`fill` can be used to fill traces.

Examples¶

Simple radar chart¶

See the entire code for this example

Here is an example that demonstrates the use of a radar chart to display the relative usage of programming languages among developers:

data = {
    # List of programming languages
    "Language": [
        "JavaScript", "HTML/CSS", "SQL", "Python",
        "Typescript", "Java", "Bash/Shell"
    ],
    # Percentage of usage, per language
    "%": [65.36, 55.08, 49.43, 48.07, 34.83, 33.27, 29.07]
}

# Close the shape for a nice-looking stroke
# If the first point is *not* appended to the end of the list,
# then the shape does not look as it is closed.
data["%"].append(data["%"][0])
data["Language"].append(data["Language"][0])

layout = {
    "polar": {
        "radialaxis": {
            # Force the radial range to 0-100
            "range": [0, 100],
        }
    },
    # Hide legend
    "showlegend": False
}

options = {
    # Fill the trace
    "fill": "toself"
}

Here is the chart control definition:

Definition

MarkdownHTMLPython

<|{data}|chart|type=scatterpolar|r=%|theta=Language|options={options}|layout={layout}|>

<taipy:chart type="scatterpolar" r="%" theta="Language" options="{options}" layout="{layout}">{data}</taipy:chart>

import taipy.gui.builder as tgb
...
tgb.chart("{data}", type="scatterpolar", r="%", theta="Language", options="{options}", layout="{layout}")

Here is the resulting figure:

Multiple data sets¶

See the entire code for this example

Radar charts are handy when used to compare two data sets: one can immediately spot where a given data set performs better or worse than another for a given category.

This example shows how to use a radar chart that displays two distinct data sets using the same categories:

# Skill categories
skills=["HTML", "CSS", "Java", "Python", "PHP", "JavaScript", "Photoshop"]
data = [
    # Proportion of skills used for Backend development
    {
        "Backend": [10, 10, 80, 70, 90, 30, 0],
        "Skills": skills
    },
    # Proportion of skills used for Frontend development
    {
        "Frontend": [90, 90, 0, 10, 20, 80, 60],
        "Skills": skills
    }
]

# Append first elements to all arrays for a nice stroke
skills.append(skills[0])
data[0]["Backend"].append(data[0]["Backend"][0])
data[1]["Frontend"].append(data[1]["Frontend"][0])

layout = {
    # Force the radial axis displayed range
    "polar": { "radialaxis": { "range": [0, 100] } }
}

# Fill the trace
options = {"fill": "toself"}

# Reflected in the legend
names = ["Backend", "Frontend"]

# To shorten the chart control definition
r     = ["0/Backend", "1/Frontend"]
theta = ["0/Skills",  "1/Skills"]

The chart definition uses all those different objects:

Definition

MarkdownHTMLPython

<|{data}|chart|type=scatterpolar|name={names}|r={r}|theta={theta}|options={options}|layout={layout}|>

<taipy:chart type="scatterpolar" name="{names}" r="{r}" theta="{theta}" options="{options}" layout="{layout}">{data}</taipy:chart>

import taipy.gui.builder as tgb
...
tgb.chart("{data}", type="scatterpolar", name="{names}", r="{r}", theta="{theta}", options="{options}", layout="{layout}")

The chart created above looks like this: