R code to generate graph of Water Levels in Ottawa

waterlevel.R

## changeing the working directory.
diegoDir='/Users/jevin/Code/personal/r/waterLevel'
setwd(diegoDir)
require(XML)

## getting the data from the web
x = readLines("http://www.ottawariver.ca/arnprior.htm")

tableNodes = getNodeSet(htmlParse(paste('</br>', x)), "//table")

tb = readHTMLTable(tableNodes[[1]], colCasses = "character")
tb2 = tb[complete.cases(tb), ]

## giving the data the right format
class(tb2)
names(tb2) = c("Year", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", "Annual Means", "Maximum", "Minimum", "Year")
head(tb2)
tb2 = tb2[-1, ]
tb2 = tb2[-c(nrow(tb2)-1, nrow(tb2)), ]

for( i in 1:ncol(tb2)){
    is.na(tb2[,i]) = which(tb2[,i] == '---')
}
tb2 = tb2[, -ncol(tb2)]

## saving data as csv
write.table(tb2, 'waterLevels.csv', sep=';', row.names=FALSE)

####################
rm(list = ls())
####################
wlevel = read.table('waterLevels.csv', sep = ';', header = TRUE)

pdf('DensityEstimationHistoricWaterLevels.pdf')
    mnths = c("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec")
    i = 1
    plot(density(wlevel[, mnths[i]], na.rm=TRUE), col = i, xlim = c(min(wlevel[, mnths], na.rm = TRUE), max(wlevel[, mnths], na.rm = TRUE)) )
    for(i in 2:length(mnths)){
        lines(density(wlevel[, mnths[i]], na.rm=TRUE), add = TRUE, col = i)
    }
    legend(x="topright", legend = mnths, col = 1:length(mnths), lwd = 1)
dev.off()


## current water Level
current = readLines("http://www.ottawariver.ca/emess.htm")
current = substr(current[grep('Chats Lake at Arnprior', current)], 91, 95)

actualMonth = months(Sys.Date(), abb=TRUE)
historic = wlevel[, actualMonth]

pdf('ActualAgainstHistoricWaterLevel.pdf')
    plot(density(historic, na.rm = TRUE), main = paste('Density estimation of historical water level at', actualMonth))
    abline(v=current, col = 'red')
    legend(x="topright", legend = "Current water level", col = 'red', lwd = 1)
dev.off()