Make separate examples proper R-style demos

Change-Id: I0ac284cfc1d0c508030c91189f260299680c1485
diff --git a/demo/frequenciesOverTime.R b/demo/frequenciesOverTime.R
new file mode 100644
index 0000000..475d2eb
--- /dev/null
+++ b/demo/frequenciesOverTime.R
@@ -0,0 +1,35 @@
+#!/usr/bin/env Rscript
+#
+# Plot frequency of query expressions over time
+#
+library(RKorAPClient)
+library(ggplot2)
+
+freqPerYear <- function(query, con = new("KorAPConnection", verbose = TRUE)) {
+  vc <- "pubDate since 2000 & pubDate until 2018 & textType = /Zeit.*/"
+  q <- corpusQuery(con, query = query, vc=vc)
+  q <- fetchAll(q)
+  tokensPerYear <- function(year) {
+    return(corpusStats(con, sprintf("%s & pubDate in %s", vc, year))@tokens)
+  }
+  df <- as.data.frame(table(as.numeric(format(q@collectedMatches$pubDate,"%Y")), dnn="year"),
+                      stringsAsFactors = FALSE)
+  df <- merge(data.frame(year=min(df$year):max(df$year)), df, all = TRUE)
+  df[is.na(df$Freq),]$Freq <- 0
+  df$total <- sapply(df$year, tokensPerYear)
+  df$freq <- df$Freq / df$total
+  df$ci <- t(sapply(Map(prop.test, df$Freq, df$total), "[[","conf.int"))
+  g <- ggplot(data = df, aes(x = year, y = freq, group=1)) +
+    geom_ribbon(aes(ymin=ci[, 1], ymax=ci[, 2]), alpha=.3) +
+    geom_point() +
+    geom_line() +
+    xlab("TIME") +
+    ylab(sprintf("Observed frequency of \u201c%s\u201d", query)) +
+    theme(axis.text.x = element_text(angle = 45, hjust = 1))
+  print(g)
+  df
+}
+#df <- freqPerYear("Car-Bikini")
+#df <- freqPerYear("[tt/p=ART & opennlp/p=ART] [tt/l=teilweise] [tt/p=NN]")
+df <- freqPerYear("Buschzulage")
+