if (FALSE) {
before_data <- selectByDate(mydata, year = 2002)
after_data <- selectByDate(mydata, year = 2003)
polarDiff(before_data, after_data, pollutant = "no2")
# with some options
polarDiff(before_data, after_data, pollutant = "no2", cols = "RdYlBu", limits = c(-20, 20))
}
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