Thanks a lot Turner.

Latter I also tried following :
oo<-quantile(original, probs = seq(0, 1, 0.01), type = 8)
pp<-quantile(predicted, probs = seq(0, 1, 0.01), type = 8)
plot(oo,pp)

But plot for above and following (as you suggested) are not same.
What may be the error ?
Thanks.

On Fri, Feb 17, 2012 at 3:01 PM, Rolf Turner <rolf.turner@xtra.co.nz> wrote:

> On 17/02/12 21:32, nandan amar wrote:
>
>> Hello,
>> I am having two data set original and predicted.
>> I want to dind QQ-plot fot it.
>> I tried in following manner :
>>
>>> qq(original~predicted)
>>>
>> and error was :
>>
>> Error in qq.formula(o ~ p) : y must have exactly 2 levels
>>
>> There is an option "qtype" which dosent make any difference.
>>
>> What is the correct way for plotting QQ-plot or am I missing something.
>>
>
> To start with, you are missing telling us that the function qq() is
> from the *lattice* package.
>
> Secondly you are missing reading the error message.  What
> does it *say*?  Think about it.
>
> It says that (rather strangely, it seems to me) that the left hand
> side of the formula must be a factor with two levels.  Obviously
> then you must combine your observations into a single vector
> and create a factor indicating to which of the two samples each
> entry of that vector belongs.  Something like:
>
>    y <- c(original,predicted)
>    f <- factor(rep(c("o","p"),c(**length(original),length(**predicted))))
>    require(lattice)
>    print(qq(f ~ y))
>
> Alternatively you could save hassle and use base graphics:
>
>    qqplot(original,predicted)
>
>    cheers,
>
>        Rolf Turner
>
>


-- 

Amar Kumar Nandan
Karnataka, India, 560100
☎:+91-9019054471
✉:nandan.amar@gmail.com
http://aknandan.co.nr

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