# create new variables

setwd('S:/Courses/stat-renaes/Stat404')
gulf=read.csv("gulf.csv",header=T)
attach(gulf)
newdist=reorder(Distance,O2,median)
plot(O2~newdist,main='Plot of Dissolved O2 vs. Distance to the Mouth of the Mississippi River')


# the ln function in R is log(variablename)

logO2=log(O2+1)
sqrtO2=sqrt(O2)
newdist2=reorder(Distance,sqrtO2,median)
newdist3=reorder(Distance,logO2,median)
plot(sqrtO2~newdist2,main="Plots of Square Root of Dissolved O2 by Distance to Mouth of Mississippi")
plot(logO2~newdist3,main="Plots of Natural Log (+1) of Dissolved O2 by Distance to Mouth of Mississippi")

# basic operations work too

mean(O2)

# mean: sum(Xi)/n
O2
sum(O2)
length(O2)
mean.O2=sum(O2)/length(O2)
mean.O2

var(O2)

# sample variance: sum(Xi-Xbar)^2/(n-1)

mean(O2)
O2-mean(O2)
sum(O2-mean(O2))
sum((O2-mean(O2))^2)
length(O2)
var.O2=sum((O2-mean(O2))^2)/(length(O2)-1)
var.O2

detach(gulf)