# Rproject7_7_kevlar.r
# 1.0 Read in data ----
# See Problem 10.9.43, data from Barlow, Toland, and Freeman (1984)
#
# Times to failure (in hours) of strands of kevlar tested at
# stress levels of 70%, 80%, and 90%.
# (The space shuttle uses spherical vessels of kevlar
# which are in an environment of sustained pressure)
kevlar70=scan(file="Rice 3e Datasets/ASCII Comma/Chapter 10/kevlar70.txt",sep=",")
kevlar80=scan(file="Rice 3e Datasets/ASCII Comma/Chapter 10/kevlar80.txt",sep=",")
kevlar90=scan(file="Rice 3e Datasets/ASCII Comma/Chapter 10/kevlar90.txt",sep=",")
# Plot the data (check for errors)
plot(kevlar70)

plot(kevlar80)

plot(kevlar90)

# 2. Compute empirical survival functions for each group ---
# 2.1 Define fcn.ecdf
# empirical cdf of time-to-failure
# Inputs
# x (times of failures)
# n (total number of items/individuals)
# For jth smallest failure, set ecdf = j/(n+1)
fcn.ecdf<-function(x, n=72){
if (sum(1*(diff(x)<0))==0){
x.0=x
x.0.ecdf=c(1:length(x.0))/(n+1)
return(x.0.ecdf)}else{return(NULL)}
}
kevlar70.esf<-1-fcn.ecdf(kevlar70,n=length(kevlar70))
kevlar80.esf<-1-fcn.ecdf(kevlar80,n=length(kevlar80))
kevlar90.esf<-1-fcn.ecdf(kevlar90,n=length(kevlar90))
# 3.0 Plot Empirical Survival Functions ---
plot(kevlar70, kevlar70.esf)

plot(kevlar80, kevlar80.esf)

plot(kevlar90, kevlar90.esf)

#
# Plots of Log Empirical Survival Functions
plot(kevlar70, log(kevlar70.esf))

plot(kevlar80, log(kevlar80.esf))

plot(kevlar90, log(kevlar90.esf))

# Re-do plot to focus on data range
plot(kevlar90, log(kevlar90.esf),xlim=c(0, 2.2))
