Draw heatmap on a python folium map

Skill - Draw heatmap on a python folium map

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Skills Required

• Setup python development environment
• Basic Printing in Python
• Commenting in Python
• Managing Variables in python
• Introduction to Folium for interactive maps in python

Please make sure to have all the skills mentioned above to understand and execute the code mentioned below. Go through the above skills if necessary for reference or revision

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In this post we will learn how to draw heatmap in folium maps using the heatmap plugin in the folium library. See this post to learn about folium libary basics.

folium heatmap plugin documentation can be found here

Simple heatmap example

import folium
from folium.plugins import HeatMap

# create a map object
mapObj = folium.Map([24.2170111233401, 81.0791015625000], zoom_start=6)

# data for heatmap. 
# each list item should be in the format [lat, long, value]
data = [
    [24.399, 80.142, 0.78],
    [22.252, 80.885, 0.68],
    [24.311, 80.543, 0.58],
    [23.195, 82.994, 0.46],
    [23.431, 80.427, 0.76],
    [26.363, 81.791, 1.81],
    [22.942, 83.257, 0.75],
    [23.751, 79.995, 0.16],
    [23.215, 81.004, 0.64],
    [24.541, 79.889, 0.55]
]

# create heatmap from the data and add to map
HeatMap(data).add_to(mapObj)

# save the map object as html
mapObj.save("output.html")

Values to be provided

• While providing the values to heatmap, re-scale the input values so that they range between 0 and 1
• 0 corresponds to least intensity, 1 corresponds to highest intensity

Values to colors mapping using the “gradient” input

By providing a dictionary to the gradient input of the heatmap, the values to color mapping can be configured

import folium
from folium.plugins import HeatMap

# create a map object
mapObj = folium.Map([24.21, 81.08], zoom_start=6)

# data for heatmap.
# each list item should be in the format [lat, long, value]
data = [
    [24.399, 80.142, 77],
    [22.252, 80.885, 50],
    [23.751, 79.995, 98],
]

# rescale each value between 0 and 1 using (val-minColorVal)/(maxColorVal-minColorVal)
# here minColorVal = 50 and maxColorVal = 100
mapData = [[x[0], x[1], (x[2]-50)/(100-50)] for x in data]

# custom color gradient
colrGradient = {0.0: 'blue',
                0.6: 'cyan',
                0.7: 'lime',
                0.8: 'yellow',
                1.0: 'red'}

# create heatmap from the data and add to map
HeatMap(mapData, gradient=colrGradient).add_to(mapObj)

# save the map object as html
mapObj.save("output.html")

Video

The video for this post can be seen here

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References

• heatmap plugin documentation - http://python-visualization.github.io/folium/plugins.html#folium.plugins.HeatMap
• default heatmap gradient colors dictionary - https://github.com/mourner/simpleheat/blob/c1998c36fa2f9a31350371fd42ee30eafcc78f9c/simpleheat.js#L22

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