# Mapbox choropleth map with customized area

**URL:** <https://community.plotly.com/t/mapbox-choropleth-map-with-customized-area/36408>\
**Category:** Plotly R\
**Created:** [March 19, 2020, 3:16pm UTC](https://community.plotly.com/t/mapbox-choropleth-map-with-customized-area/36408 "2020-03-19T15:16:41Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![changhc](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@changhc](https://community.plotly.com/u/changhc)\
**Post date:** [March 19, 2020, 3:16pm UTC](https://community.plotly.com/t/mapbox-choropleth-map-with-customized-area/36408/1 "2020-03-19T15:16:41Z")

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Hi,

I try to make a choropleth map for the orange part in the following plot.

 ![nnOTK](https://us1.discourse-cdn.com/flex024/uploads/plot/original/2X/2/211abcbf93963eafd7b97e0ed8e7e6247fb96b48.png)  
This scattermapbox is salt concentration (data from NASA resolution is 0.625 \* 0.5) and I set the condition that salt concentration should be higher than a certain level so finally I have this plot.  
I found some examples which deal with countries or counties. For my problem here, I only have the geographic coordinates and the region is kind of random.  
As I understand, the idea of choropleth is to color a region with its boundaries’ coordinates but I don’t know how to generate the geo file.  
Any comments will be appreciated!

Thank you!

Chang