F-distribution and t-distribution

Fdist_tdist.R

df1<-1
df2<-100
critF<-qf(.95, df1=df1, df2=df2) #determine critical F-value
critT<-qt(.975, df2) #determine critical F-value
critF #critical F-value
critT^2 #Critical t squared is the same as critical F-value
critT #critical t-value

x=seq(0,10,length=10000)
maxy<-ifelse(max(df(x,df1,df2))==Inf,1, max(df(x,df1,df2))) #set maximum y axis

#png(file=paste('Fdist.png'),width=8000,height=4000, res = 750)
plot(x,df(x,df1,df2),col='black',type='l', lwd=2, xlim=c(0,8), ylim=c(0,maxy), xlab="F- or t-value", ylab="Density",main=paste("F-distribution, df1 = ",df1,", df2 = ",df2), xaxt="n",yaxt="n")
x=seq(critF,10,length=10000) 
z<-(df(x,df1,df2)) #determine upperbounds polygon
polygon(c(critF,x,10),c(0,z,0),col="skyblue") #draw polygon
x=seq(0,8,length=10000)
lines(x,dt(x,df=df2),col='palegreen4',type='l',lwd=2)
x=seq(critT,10,length=10000) 
z<-(dt(x,df=df2)) #determine upperbounds polygon
polygon(c(critT,x,10),c(0,z,0),col="palegreen2")
axis(1, at = seq(0, 8, by = 1))
#dev.off()