Ghent air quality study VMM rehash

ghent_air_quality_vmm.R

# Ghent air pollution analysis
# parametric t-tests
# non-parametric Mann-Whitney U test

# download and collate the data
pdf_data <- paste0(pdftools::pdf_text("https://klimaat.stad.gent/sites/default/files/nota_circulatieplangent_3.pdf")[2],
               collapse = " ")

# some regular expression moving about
subset <- gsub(',', ".", pdf_data)
subset <- gsub('\n', "  ", subset)
subset <- unlist(strsplit(subset, "\\s{2,}"))[10:129]

# recast into a data frame
df <- data.frame(matrix(subset, 20,6, byrow = TRUE),
                    stringsAsFactors = FALSE)

# assign column names
names(df) <- c("meetplaatscode",
               "straat",
               "voor",
               "na",
               "verschil",
               "verschil_perc")

# convert to numeric
df$voor <- as.numeric(df$voor)
df$na <- as.numeric(df$na)
df$verschil <- as.numeric(df$verschil)

# test for normality
s_test <- shapiro.test(df$verschil)

# t-test on the difference
t.test(df$voor, df$na)
t.test(df$voor, df$na + 3.7)

# non-parametric t-test
wilcox.test(df$voor, df$na)
wilcox.test(df$voor, df$na + 3.7)