folium.colormap
¶A few examples of how to use folium.colormap
in choropleths.
import pandas as pd
import json
import sys
sys.path.append('..')
import folium
print (folium.__file__)
print (folium.__version__)
../folium/__init__.py 0.2.0.dev
Let's load a GeoJSON file, and try to choropleth it.
geo_json_data = json.load(open('us-states.json'))
unemployment = pd.read_csv('./US_Unemployment_Oct2012.csv')
unemployment_dict = unemployment.set_index('State')['Unemployment']
You can build a choropleth in using a self-defined function.
It has to output an hexadecimal color string of the form #RRGGBB
or #RRGGBBAA
.
def my_color_function(feature):
"""Maps low values to green and hugh values to red."""
if unemployment_dict[feature['id']] > 6.5:
return '#ff0000'
else:
return '#008000'
m = folium.Map([43,-100], tiles='cartodbpositron', zoom_start=4)
folium.GeoJson(
geo_json_data,
style_function=lambda feature: {
'fillColor': my_color_function(feature),
'color' : 'black',
'weight' : 2,
'dashArray' : '5, 5'
}
).add_to(m)
m
But to help you define you colormap, we've embedded StepColormap
in folium.colormap
.
You can simply define the colors you want, and the index
(thresholds) that correspond.
import folium.colormap as cm
step = cm.StepColormap(['green','yellow','red'], vmin=3., vmax=10., index=[3,4,8,10], caption='step')
step
m = folium.Map([43,-100], tiles='cartodbpositron', zoom_start=4)
folium.GeoJson(
geo_json_data,
style_function=lambda feature: {
'fillColor': step(unemployment_dict[feature['id']]),
'color' : 'black',
'weight' : 2,
'dashArray' : '5, 5'
}
).add_to(m)
m
If you specify no index, colors will be set uniformely.
cm.StepColormap(['r','y','g','c','b','m'])
But sometimes, you would prefer to have a continuous set of colors. This can be done by LinearColormap
.
linear = cm.LinearColormap(['green','yellow','red'], vmin=3., vmax=10.)
linear
m = folium.Map([43,-100], tiles='cartodbpositron', zoom_start=4)
folium.GeoJson(
geo_json_data,
style_function=lambda feature: {
'fillColor': linear(unemployment_dict[feature['id']]),
'color' : 'black',
'weight' : 2,
'dashArray' : '5, 5'
}
).add_to(m)
m
Again, you can set the index
if you want something irregular.
cm.LinearColormap(['red','orange', 'yellow','green'], index=[0,0.1,0.9,1.])
If you want to transform a linear map into a step one, you can use the method to_step
.
linear.to_step(6)
You can also use more sophisticated rules to create the thresholds.
linear.to_step(6,
data=[30.6, 50, 51, 52, 53, 54, 55, 60, 70, 100],
method='quantiles',
round_method='int')
And the opposite is also possible with to_linear
.
step.to_linear()
For convenience, we provide a (small) set of built-in linear colormaps, in folium.colormap.linear
.
cm.linear.OrRd
You can also use them to generate regular StepColormap
.
cm.linear.PuBu.to_step(12)
Of course, you may need to scale the colormaps to your bounds. This is doable with .scale
.
cm.linear.YlGn.scale(3,12)
cm.linear.RdGy.to_step(10).scale(5,100)
At last, if you want to check them all, simply ask for linear
in the notebook.
cm.linear
YlOrBr | |
Paired | |
PuOr | |
Pastel2 | |
Pastel1 | |
YlGn | |
PRGn | |
GnBu | |
YlGnBu | |
RdBu | |
RdGy | |
BuPu | |
RdYlGn | |
Accent | |
RdYlBu | |
Spectral | |
PuRd | |
BuGn | |
RdPu | |
Set3 | |
PuBuGn | |
Set2 | |
Set1 | |
BrBg | |
PuBu | |
Dark2 | |
OrRd | |
PiYG | |
YlOrRd |
ColorMap
on a map¶By the way, a ColorMap is also a Folium Element
that you can draw on a map.
m = folium.Map(tiles='cartodbpositron')
colormap = cm.linear.Set1.scale(0,35).to_step(10)
colormap.caption = 'A colormap caption'
m.add_children(colormap)
m
That's all folks !
Hope it'll be useful to you. Don't hesitate to provide a feedback on what can be improved, which method do you prefer, etc.