# [R] qqplot for binomial distribution

Ashim Kapoor ashimkapoor at gmail.com
Wed Apr 19 09:02:57 CEST 2017

```Dear Boris,

Many thanks,
Ashim

On Tue, Apr 18, 2017 at 7:56 PM, Boris Steipe <boris.steipe at utoronto.ca>
wrote:

> As per the help pages, the data samples are expected in the second
> argument, "y".
>
> So try
>   qqplot(rbinom(n=100, size=100, p=0.05), count1_vector)
>
> ... and then plot your qqline()
>
> Alternatively, try
>
> qqline(count1_vector,
>        distribution = function(probs) { qbinom(probs, size=100, prob=0.05)
> },
>        datax = TRUE, # <- logical. Should data values be on the x-axis?
>        col = "red",
>        lwd = 0.5)
> ... and use your original qqplot()
>
>
> B.
>
>
> > On Apr 18, 2017, at 12:47 AM, Ashim Kapoor <ashimkapoor at gmail.com>
> wrote:
> >
> > Dear Boris,
> >
> >
> > > dput(count1_vector)
> > c(5, 6, 4, 4, 6, 5, 4, 5, 3, 7, 5, 5, 3, 4, 8, 6, 10, 2, 4, 6,
> > 8, 4, 4, 6, 8, 5, 6, 3, 7, 9, 4, 7, 5, 7, 3, 4, 5, 2, 11, 7,
> > 8, 5, 5, 6, 3, 2, 3, 5, 9, 6, 5, 6, 7, 3, 10, 7, 6, 4, 9, 5,
> > 7, 3, 7, 3, 2, 3, 4, 5, 10, 4, 5, 5, 6, 7, 4, 8, 7, 5, 5, 4,
> > 8, 7, 9, 4, 4, 4, 7, 5, 4, 10, 4, 5, 6, 1, 3, 5, 4, 7, 4, 6)
> >
> > set.seed(123)
> > qqplot(count1_vector,rbinom(n=100,size=100,p=.05))
> > qqline(count1_vector,distribution = function(probs) { qbinom(probs,
> size=100, prob=0.05) },
> >        col = "red",
> >        lwd = 0.5)
> >
> > When I do this, the line does not pass through the center of my data.I
> do expect count1_vector to be 100 samples of binomial with n=100 and p=.05.
> >
> > Any comments or suggestions for me ?
> >
> > Note : I built a 95% Confidence interval for my data and I counted how
> often out of 100 times did the data fall outside the CI.This I expect to be
> binomial with n=100,p=.05. I repeated this a 100 times and obtained
> count1_vector.
> >
> > Best Regards,
> > Ashim.
> >
> >
> > On Mon, Apr 17, 2017 at 7:51 PM, Boris Steipe <boris.steipe at utoronto.ca>
> wrote:
> > That's not how qqline() works. The line is drawn with respect to a
> _reference_distribution_ which is the normal distribution by default. For
> the binomial distribution, you need to specify the distribution argument.
> There is an example in the help page that shows you how this is done for
> qchisq(). for qbinom() it is:
> >
> >
> > set.seed(123)
> > qqplot(rbinom(n=100, size=100, p=0.05),
> >        rbinom(n=100, size=100, p=0.05) )
> >
> > qqline(rbinom(n=100,size=100,p=.05),
> >        distribution = function(probs) { qbinom(probs, size=100,
> prob=0.05) },
> >        col = "red",
> >        lwd = 0.5)
> >
> >
> >
> >
> > B.
> >
> >
> > > On Apr 17, 2017, at 9:15 AM, Ashim Kapoor <ashimkapoor at gmail.com>
> wrote:
> > >
> > > Dear Spencer,
> > >
> > > Okay. Many thanks. My next query is how do I use qqline?
> > >
> > > When I try
> > >
> > >> qqline(rbinom(n=100,size=100,p=.05))
> > >
> > > I don't get the line in the right place.
> > >
> > > Best Regards,
> > > Ashim
> > >
> > > On Mon, Apr 17, 2017 at 6:31 PM, Spencer Graves <
> > > spencer.graves at effectivedefense.org> wrote:
> > >
> > >>
> > >>
> > >> On 2017-04-17 7:58 AM, Ashim Kapoor wrote:
> > >>
> > >>> Dear All,
> > >>>
> > >>> set.seed(123)
> > >>> qqplot(rbinom(n=100,size=100,p=.05), rbinom(n=100,size=100,p=.05) )
> > >>>
> > >>> I expect to see 1 clear line,but I don't. What am I misunderstanding?
> > >>>
> > >>
> > >>
> > >>      The distribution is discrete, and points are superimposed. Try
> the
> > >> following:
> > >>
> > >>
> > >> set.seed(123)
> > >> qqplot(jitter(rbinom(n=100,size=100,p=.05)),
> > >>       jitter(rbinom(n=100,size=100,p=.05) ))
> > >>
> > >>
> > >>      Spencer Graves
> > >>
> > >>>
> > >>> Best Regards,
> > >>> Ashim
> > >>>
> > >>>        [[alternative HTML version deleted]]
> > >>>
> > >>> ______________________________________________
> > >>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > >>> https://stat.ethz.ch/mailman/listinfo/r-help
> > >>> ng-guide.html
> > >>> and provide commented, minimal, self-contained, reproducible code.
> > >>>
> > >>
> > >> ______________________________________________
> > >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > >> https://stat.ethz.ch/mailman/listinfo/r-help
> > >> ng-guide.html
> > >> and provide commented, minimal, self-contained, reproducible code.
> > >>
> > >
> > >       [[alternative HTML version deleted]]
> > >
> > > ______________________________________________
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> > > https://stat.ethz.ch/mailman/listinfo/r-help