####################################################################
## Unix:
## /usr/bin/R -q --no-restore --no-save < telstra.r
## DOS:
## "S:\\R\\rw2001\\bin\\Rterm.exe" -q --no-restore --no-save < telstra.r 
####################################################################

options(echo = FALSE)

#--------------------------------------------------------------------
# Enter series name:

seriesname = "OLEAUSPZZP";

write(paste("series:",seriesname),file="");

bitmap(file=paste(seriesname,"png",sep="."),width=5,height=5,res=400)
#png(file=seriesname,width=680,height=450,pointsize=12,bg="white",res=200); 

#--------------------------------------------------------------------
# Read/store data:

data <- scan(paste(seriesname,"txt",sep="."), list(0,0));

x <- data[[1]];
y <- data[[2]];

#--------------------------------------------------------------------
# Store into ts objects and plot.

startyear <- 2004;
startperiod <- 1;
freq <- 4;
xts <- ts( x, start=c(startyear, startperiod), frequency=freq ); 
yts <- ts( y, start=c(startyear, startperiod), frequency=freq );

ts.plot(xts, yts, gpars=list(ylab="Value", col=c(1:2)), 
        main=paste("series:",seriesname));

#--------------------------------------------------------------------
# Compute ratio: R=x/y and test for H0: R=1 vs H1: R>1(public) or R<1(private) 
# Apply 1-sided t-test.

R <- x / y; 
tvalue <- (mean(R) - 1) / (sd(R)/sqrt(length(R))); 

# probability of obtaining value > this observed tvalue 
# (i.e. R > observed x/y) by chance is:

if( (mean(R) > 1) && (median(R) > 1) ) {
  pvalue <- pt(tvalue, (length(R)-1), lower.tail=FALSE);
} else if( (mean(R) < 1) && (median(R) < 1) ) {
  pvalue <- pt(tvalue, (length(R)-1), lower.tail=TRUE);
} else { 
  write(paste("Disaster! Check vector of ratios:"), file="");
  R;
  mean(R);
  median(R);
  q();
}

# if then say pvalue < 0.05 (5%), observed R is very unlikely
# to be due to chance occurance - not consistent with R=1 hence
# reject H0. 

# echo results to screen:
R;
tvalue;
pvalue;
mean(R);
median(R);

dev.off();
q();