[R] qqplot

[Yihui Xie]

abline(0,1) is somewhere in the upper-left corner which you are unable
to see. At least the first distribution seems to have a larger mean
than the second one (i.e. they are not the same distribution).

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
Phone: 515-294-6609 Web: http://yihui.name
Department of Statistics, Iowa State University
3211 Snedecor Hall, Ames, IA



On Mon, Nov 2, 2009 at 10:33 AM, carol white <wht_crl at yahoo.com> wrote:
> if I have the two following matrices, abline(0,1) doesn't go through. QQplot is attached.
>
>            [,1]     [,2]     [,3]     [,4]     [,5]
>  2.149644 1.992864 3.346375 2.793511 3.428230
>  1.100762 2.152981 2.735401 2.175185 3.323058
> 1.212406 2.131813 2.672598 2.389996 3.242490
> 1.183770 1.908633 2.661237 2.590545 2.906059
>  1.665190 1.778923 2.636062 2.475619 4.013407
>
>
>    0.601   0.083   0.520    0.920  -0.007
>   -0.778   0.427  -0.605   -0.066  -0.283
>  -0.599   0.348  -0.693    0.284  -0.436
>   -0.519   0.081  -0.590    0.678  -1.095
>    0.009  -0.253  -0.940    0.526   1.623
>
>
> --- On Mon, 11/2/09, David Winsemius <dwinsemius at comcast.net> wrote:
>
>> From: David Winsemius <dwinsemius at comcast.net>
>> Subject: Re: [R] qqplot
>> To: "carol white" <wht_crl at yahoo.com>
>> Cc: r-help at stat.math.ethz.ch
>> Date: Monday, November 2, 2009, 8:17 AM
>>
>> On Nov 2, 2009, at 10:40 AM, carol white wrote:
>>
>> > Hi,
>> > We could use qqplot to see how two distributions are
>> different from each other. To show better how they are
>> different (departs from the straight line), how is it
>> possible to plot the straight line that goes through them? I
>> am looking for some thing like qqline for qqnorm. I thought
>> of abline but how to determine the slope and intercept?
>>
>> I always assumed that the intercept was zero and the slope
>> = unity.
>>
>>  y <- rt(200, df = 5)
>>  qqnorm(y); qqline(y, col = 2)
>>  qqplot(y, rt(300, df = 5))
>>  abline(0, 1, col="red")
>>
>> I am open to education if that assumption is too
>> simplistic, but you have not offered anything in the way of
>> a counter-example.
>>
>> >
>> ==
>>
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>>
>>
>
>
>
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