Hi Ali:
Try this for the Chi-Square test statistic.
good luck
abou
###############################################################
par(mfrow = c(1,2))
shade.dchisq <- function(df,ncp,a,b, Col="red"){
#add to plot of normal density, shading area between a and b
n <- 100
x <- seq(a,b,length=n)
y <- dchisq(x,df,ncp)
X = c(x[1],x,x[n])
Y =c(0,y,0)
polygon(X,Y,col=Col)
}
shade.dchisq1 <- function(df,ncp,a,b, density=30){
#add to plot of chi-square density, shading area between a and b
n <- 100
x <- seq(a,b,length=n)
y <- dchisq(x,df,ncp)
X = c(x[1],x,x[n])
Y =c(0,y,0)
polygon(X,Y,density=density)
}
#### example:
x <- seq(0,20,.01)
y <- dchisq(x,3,0) ### df=5, ncp=0
x1<-seq(0,20,0.01)
y1<-dchisq(x,3,2) ### df=5, ncp=2
plot(x,y,type="l", ylab="density", lwd=3,col="red") ### xlim=c(-7,10),
#### title(main="Distributions of T under H0 and Ha")
title(main=" Distributions of T")
lines(x1,y1,lwd=3, col="blue")
shade.dchisq1(3,2,9,20,30)
shade.dchisq(3,0,9,20)
abline(h=0,lwd=3)
#### add legend
chicurve<-c("nc=0","nc=2")
legend(list(x=9,y=0.23), legend = chicurve, col=c("red","blue"), cex=1.0,
lwd=2, lty=1, merge=TRUE)#, trace=TRUE)
#################################### Chi-Square test
###########################
shade.dchisq <- function(df,ncp,a,b, Col="red"){
#add to plot of normal density, shading area between a and b
n <- 100
x <- seq(a,b,length=n)
y <- dchisq(x,df,ncp)
X = c(x[1],x,x[n])
Y =c(0,y,0)
polygon(X,Y,col=Col)
}
shade.dchisq1 <- function(df,ncp,a,b, density=30){
#add to plot of chi-square density, shading area between a and b
n <- 100
x <- seq(a,b,length=n)
y <- dchisq(x,df,ncp)
X = c(x[1],x,x[n])
Y =c(0,y,0)
polygon(X,Y,density=density)
}
#### example:
x <- seq(0,20,.01)
y <- dchisq(x,3,0) ### df=3, ncp=0
x1<-seq(0,20,0.01)
y1<-dchisq(x,3,5) ### df=3, ncp=5
plot(x,y,type="l", ylab="density", lwd=3,col="red") ### xlim=c(-7,10),
##### title(main="Distributions of T under H0 and Ha")
title(main="under H0 and Ha ")
lines(x1,y1,lwd=3, col="blue")
shade.dchisq1(3,5,9,20,30)
shade.dchisq(3,0,9,20)
abline(h=0,lwd=3)
#### add legend
chicurve<-c("nc=0","nc=5")
legend(list(x=9,y=0.23), legend = chicurve, col=c("red","blue"), cex=1.0,
lwd=2, lty=1, merge=TRUE)#, trace=TRUE)
################################################################
==========================
AbouEl-Makarim Aboueissa, Ph.D.
Associate Professor of Statistics
Graduate Program Coordinator
Department of Mathematics & Statistics
University of Southern Maine
96 Falmouth Street
P.O. Box 9300
Portland, ME 04104-9300
USA
Tel: (207) 228-8389
Fax: (207) 780-5607
Email: [email protected]
[email protected]
Office: 301C Payson Smith
>>> Ali Zanaty <[email protected]> 4/15/2012 11:14 AM >>>
Dear All:
I need a quick help in R. How I can plot plot the distribution of the T test
statistic under Ho and Ha with shading areas. Plot overlapping two T
distributions and shading overlapping areas under both curves. You choose any
values just
for example. I could not upload any graph for example.
Once I know how to create this one, I think I will be able to create the one
for normal case.
Thank you very much and sorry for bothering.
Ali
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