Using colormaps#
A few examples of how to use folium.colormap in choropleths.
Let’s load a GeoJSON file, and try to choropleth it.
[2]:
import pandas
import requests
geo_json_data = requests.get(
"https://raw.githubusercontent.com/python-visualization/folium-example-data/main/us_states.json"
).json()
unemployment = pandas.read_csv(
"https://raw.githubusercontent.com/python-visualization/folium-example-data/main/us_unemployment_oct_2012.csv"
)
unemployment_dict = unemployment.set_index("State")["Unemployment"]
Self-defined#
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.
[3]:
def my_color_function(feature):
"""Maps low values to green and high values to red."""
if unemployment_dict[feature["id"]] > 6.5:
return "#ff0000"
else:
return "#008000"
[4]:
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
[4]:
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StepColormap#
But to help you define your colormap, we’ve embedded StepColormap in folium.colormap.
You can simply define the colors you want, and the index (thresholds) that correspond.
[5]:
import branca.colormap as cm
step = cm.StepColormap(
["green", "yellow", "red"], vmin=3, vmax=10, index=[3, 4, 8, 10], caption="step"
)
step
[5]:
[6]:
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
[6]:
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If you specify no index, colors will be set uniformly.
[7]:
cm.StepColormap(["r", "y", "g", "c", "b", "m"])
[7]:
LinearColormap#
But sometimes, you would prefer to have a continuous set of colors. This can be done by LinearColormap.
[8]:
linear = cm.LinearColormap(["green", "yellow", "red"], vmin=3, vmax=10)
linear
[8]:
[9]:
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
[9]:
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Again, you can set the index if you want something irregular.
[10]:
cm.LinearColormap(["red", "orange", "yellow", "green"], index=[0, 0.1, 0.9, 1.0])
[10]:
If you want to transform a linear map into a step one, you can use the method to_step.
[11]:
linear.to_step(6)
[11]:
You can also use more sophisticated rules to create the thresholds.
[12]:
linear.to_step(
n=6,
data=[30.6, 50, 51, 52, 53, 54, 55, 60, 70, 100],
method="quantiles",
round_method="int",
)
[12]:
And the opposite is also possible with to_linear.
[13]:
step.to_linear()
[13]:
Built-in#
For convenience, we provide a (small) set of built-in linear colormaps, in folium.colormap.linear.
[14]:
cm.linear.OrRd_09
[14]:
You can also use them to generate regular StepColormap.
[15]:
cm.linear.PuBuGn_09.to_step(12)
[15]:
Of course, you may need to scale the colormaps to your bounds. This is doable with .scale.
[16]:
cm.linear.YlGnBu_09.scale(3, 12)
[16]:
[17]:
cm.linear.RdGy_11.to_step(10).scale(5, 100)
[17]:
At last, if you want to check them all, simply ask for linear in the notebook.
[18]:
cm.linear
[18]:
| viridis | |
| plasma | |
| inferno | |
| magma | |
| Pastel1_03 | |
| Pastel1_05 | |
| Pastel1_04 | |
| Pastel1_07 | |
| YlOrRd_04 | |
| Pastel1_09 | |
| Pastel1_08 | |
| Spectral_07 | |
| RdYlBu_05 | |
| PuBuGn_03 | |
| Set1_08 | |
| PuBuGn_05 | |
| PuBuGn_04 | |
| PuBuGn_07 | |
| PuBuGn_06 | |
| PuBuGn_09 | |
| PuBuGn_08 | |
| YlOrBr_04 | |
| YlOrBr_05 | |
| Set1_07 | |
| YlOrBr_03 | |
| Set1_05 | |
| YlOrRd_03 | |
| PuOr_06 | |
| PuOr_07 | |
| PuOr_04 | |
| PuOr_05 | |
| PuOr_03 | |
| Purples_09 | |
| Set2_06 | |
| RdYlBu_11 | |
| PuOr_08 | |
| PuOr_09 | |
| Paired_03 | |
| RdBu_03 | |
| RdYlBu_10 | |
| Paired_07 | |
| Paired_06 | |
| Paired_05 | |
| Paired_04 | |
| Paired_09 | |
| Paired_08 | |
| RdGy_03 | |
| PiYG_04 | |
| Accent_03 | |
| BuGn_08 | |
| BuGn_09 | |
| BuGn_04 | |
| BuGn_05 | |
| BuGn_06 | |
| BuGn_07 | |
| BuGn_03 | |
| YlGnBu_07 | |
| YlGnBu_06 | |
| YlGnBu_05 | |
| YlGnBu_04 | |
| YlGnBu_03 | |
| RdBu_06 | |
| RdBu_05 | |
| RdBu_04 | |
| Accent_08 | |
| RdBu_09 | |
| RdBu_08 | |
| Set2_04 | |
| YlGnBu_09 | |
| YlGnBu_08 | |
| Blues_08 | |
| Blues_09 | |
| RdPu_09 | |
| RdPu_08 | |
| Set3_07 | |
| Set3_06 | |
| RdPu_05 | |
| RdPu_04 | |
| RdPu_07 | |
| RdPu_06 | |
| Blues_06 | |
| Blues_07 | |
| RdPu_03 | |
| Blues_05 | |
| Paired_10 | |
| Paired_11 | |
| Paired_12 | |
| PuBu_06 | |
| PuBu_07 | |
| PuBu_04 | |
| PuBu_05 | |
| PuRd_05 | |
| PuBu_03 | |
| PuRd_07 | |
| PuRd_06 | |
| PuRd_09 | |
| PuRd_08 | |
| Set2_07 | |
| PuBu_08 | |
| PuBu_09 | |
| RdBu_10 | |
| RdBu_11 | |
| Accent_06 | |
| Set3_03 | |
| Set3_05 | |
| Set3_12 | |
| Set3_10 | |
| Set3_04 | |
| RdGy_11 | |
| RdGy_10 | |
| Set1_03 | |
| Set1_09 | |
| Set3_09 | |
| BuPu_08 | |
| BuPu_09 | |
| RdYlGn_11 | |
| Blues_03 | |
| Set2_05 | |
| BuPu_03 | |
| BuPu_06 | |
| BuPu_07 | |
| BuPu_04 | |
| BuPu_05 | |
| Accent_04 | |
| YlOrRd_05 | |
| YlOrBr_08 | |
| Oranges_08 | |
| Oranges_09 | |
| Oranges_06 | |
| Oranges_07 | |
| Oranges_04 | |
| YlOrBr_09 | |
| Oranges_03 | |
| YlOrBr_06 | |
| Dark2_06 | |
| Blues_04 | |
| YlOrBr_07 | |
| RdYlGn_05 | |
| Set3_08 | |
| YlOrRd_06 | |
| Dark2_03 | |
| Accent_05 | |
| RdYlGn_08 | |
| RdYlGn_09 | |
| PuOr_11 | |
| YlOrRd_07 | |
| Spectral_11 | |
| RdGy_08 | |
| RdGy_09 | |
| RdGy_06 | |
| RdGy_07 | |
| RdGy_04 | |
| RdGy_05 | |
| RdYlGn_04 | |
| PiYG_09 | |
| RdYlGn_06 | |
| RdYlGn_07 | |
| Spectral_04 | |
| Spectral_05 | |
| Spectral_06 | |
| PiYG_08 | |
| Set2_03 | |
| Spectral_03 | |
| Reds_08 | |
| Set1_04 | |
| Spectral_08 | |
| Spectral_09 | |
| Set2_08 | |
| Reds_09 | |
| Greys_07 | |
| Greys_06 | |
| Greys_05 | |
| Greys_04 | |
| Greys_03 | |
| PuOr_10 | |
| Accent_07 | |
| Reds_06 | |
| Greys_09 | |
| Greys_08 | |
| Reds_07 | |
| RdYlBu_08 | |
| RdYlBu_09 | |
| BrBG_09 | |
| BrBG_08 | |
| BrBG_07 | |
| BrBG_06 | |
| BrBG_05 | |
| BrBG_04 | |
| BrBG_03 | |
| PiYG_06 | |
| Reds_03 | |
| Set3_11 | |
| Set1_06 | |
| PuRd_03 | |
| PiYG_07 | |
| RdBu_07 | |
| Pastel1_06 | |
| Spectral_10 | |
| PuRd_04 | |
| OrRd_03 | |
| PiYG_03 | |
| Oranges_05 | |
| OrRd_07 | |
| OrRd_06 | |
| OrRd_05 | |
| OrRd_04 | |
| Reds_04 | |
| Reds_05 | |
| OrRd_09 | |
| OrRd_08 | |
| BrBG_10 | |
| BrBG_11 | |
| PiYG_05 | |
| YlOrRd_08 | |
| GnBu_04 | |
| GnBu_05 | |
| GnBu_06 | |
| GnBu_07 | |
| Purples_08 | |
| GnBu_03 | |
| Purples_06 | |
| Purples_07 | |
| Purples_04 | |
| Purples_05 | |
| GnBu_08 | |
| GnBu_09 | |
| YlOrRd_09 | |
| Purples_03 | |
| RdYlBu_04 | |
| PRGn_09 | |
| PRGn_08 | |
| PRGn_07 | |
| PRGn_06 | |
| PRGn_05 | |
| PRGn_04 | |
| PRGn_03 | |
| RdYlBu_06 | |
| RdYlGn_10 | |
| YlGn_08 | |
| YlGn_09 | |
| RdYlBu_07 | |
| PiYG_10 | |
| PiYG_11 | |
| YlGn_03 | |
| YlGn_04 | |
| YlGn_05 | |
| YlGn_06 | |
| YlGn_07 | |
| Dark2_05 | |
| Dark2_04 | |
| Dark2_07 | |
| Pastel2_03 | |
| Pastel2_04 | |
| Pastel2_05 | |
| Pastel2_06 | |
| Pastel2_07 | |
| Pastel2_08 | |
| RdYlBu_03 | |
| Dark2_08 | |
| RdYlGn_03 | |
| PRGn_11 | |
| Greens_08 | |
| Greens_09 | |
| Greens_06 | |
| Greens_07 | |
| Greens_04 | |
| Greens_05 | |
| PRGn_10 | |
| Greens_03 |
Draw a ColorMap on a map#
By the way, a ColorMap is also a Folium Element that you can draw on a map.
[19]:
m = folium.Map(tiles="cartodbpositron")
colormap = cm.linear.Set1_09.scale(0, 35).to_step(10)
colormap.caption = "A colormap caption"
m.add_child(colormap)
m
[19]:
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