Question

I want to confirm that my data is fit on the Poisson distribution or not. I think I should use qqplot, but I can't figure out how show it by R code

count	frequency
0	229
1	221
2	93
3	35
4	7
7	1

Answer 1

:Use the following code to plot qqplot

#import excel file of data in R

>D1=read.table("<FileName>.txt",header = TRUE)

Attach(D1)

>ybar=mean(D1)

> p=ncol(D1)

> sig=matrix(nrow=p,ncol=p)

> for(i in 1:p)

+ {

+ for(j in 1:p)

+ {

+ sig[i,j]=cov(D1[,i],D1[,j])

+ }

+ }

> sig

> #to find sample quantiles

> chisq=c()

> for(i in 1:n)

+ {

+ chisq[i]=t(D1[i,]-ybar)%*%solve(sig)%*%(D1[i,]-ybar)

+ }

> chisq

> sq=sort(chisq)

> #to find population quantiles

> i=1:n

> s=(i-0.5)/n

> pq=qchisq(s,p)

> #QQ plot

> plot(sq,pq)

> abline(0,1)

#Output given following