Tests the hypothesis that vigesimal (base-20) number systems are more common at tropical latitudes

WALS131A.R

#!/usr/bin/env Rscript
# WALS131A.R
# Kyle Gorman <kylebgorman@gmail.com>
# 
# Tests the hypothesis that vigesimal (base-20) number systems are more common
# at tropical latitudes. Thanks to Richard Sproat for suggesting this
# hypothesis.
# 
# The data is read directly from WALS (#131A):
# 
# Dryer, Matthew S. and Haspelmath, Martin (eds.). 2013. The World Atlas of
# Language Structure Online. Max Planck Institute for Evolutionary
# Anthropology. URL: http://wals.info.

URL <- "http://wals.info/feature/131A.tab"
SKIP <- 5  # First five rows are documentation.

d <- droplevels(subset(read.table(URL, sep="\t", header=TRUE, skip=SKIP),
                       value < 4))

cat(sprintf("\nCounts:\n"))
print(table(d$description))

# Our independent variable: absolute latitude.
d$absolute.latitude <- abs(d$latitude)
cat(sprintf("\nMedian absolute latitude:\n\n"))
print(with(d, tapply(absolute.latitude, description, median)))

# Simple models.
wt <- with(subset(d, value < 3),
           suppressWarnings(wilcox.test(absolute.latitude ~ value)))
cat(sprintf("\n"))
cat(sprintf("Decimal vs. hybrid:\tW = %.1f,\tp = %.3f\n",
            wt$statistic, wt$p.value))
wt <- with(subset(d, value > 1),
           suppressWarnings(wilcox.test(absolute.latitude ~ value)))
cat(sprintf("Hybrid vs. vigesimal:\tW = %.1f,\tp = %.3f\n",
            wt$statistic, wt$p.value))
wt <- with(d, suppressWarnings(wilcox.test(absolute.latitude ~ value < 2)))
cat(sprintf("Decimal vs. other:\tW = %.1f,\tp = %.3f\n",
            wt$statistic, wt$p.value))
wt <- with(d, suppressWarnings(wilcox.test(absolute.latitude ~ value < 3)))
cat(sprintf("Vigesimal vs. other:\tW = %.1f,\tp = %.3f\n",
            wt$statistic, wt$p.value))