I used the Cooperative Clergy Election Study, 2016 to do the analysis.
The numbers you are seeing are the percent of white evangelicals who say that they attend seldom or never.
Brighter yellow = more nominal evangelicals. Darker greenish-blue = fewer nominal evangelicals.
You can mouse over any state and a popup will come with the percent of evangelicals who say they attend seldom or never.
## OGR data source with driver: GeoJSON
## Source: "state.json", layer: "OGRGeoJSON"
## with 52 features
## It has 5 fields