Y<-function(x1,x2) 25+3*x1+4*x2+1.5*x1*x2
x=seq(0,7)
EY=Y(x,3)
plot(x,EY,type = "l",col=4)
abline(49,12,col=2)
x1=seq(-10,10,0.5)
x2=seq(-10,10,0.5)
z=outer(x1,x2,Y)
contour(x1,x2,z)
data=read.table("D:CH08TA02.txt",header=T)
attach(data)
fm=lm(Y~x2)
xtable(summary(fm))
concentration=read.table("D:concentration.txt",header=T)
attach(concentration)
concentration.lm<-lm(Y~X)
boxcox(concentration.lm)
boxcox(concentration.lm,lambda=seq(-0.3,0.3,0.1))
machine=read.table("D:CH11PR07.txt",header=T)
attach(machine)
fm1=lm(Y~x)
xtable(summary(fm1))
par(mfrow=c(2,2))
plot(fm1)
res=residuals(fm1)
plot(x,res^2)
fm2=lm(res^2~x)
xtable((summary(fm2)))
wi=1/fitted(fm2)
print(cbind(x,Y,res,"res^2"=res^2,weights=wi),digits=2)
fm3=lm(Y~x,weights=wi)
xtable(summary(fm3))