Hello ALL! Can anyone tell me how to specify qqmath() function with distribution qgamma? In help it is bit vague how to pass shape and scale parameters for gamma. Thank you in advance. Best, PM
On 9/4/2009 8:36 AM, Petar Milin wrote:> Hello ALL! > Can anyone tell me how to specify qqmath() function with distribution > qgamma? > In help it is bit vague how to pass shape and scale parameters for gamma.Take a look at the first example, which passes in the df parameter for a t distribution. You want something like x <- runif(1000) # not a gamma, plot should look bad qqmath(~ x, distribution=function(x) qgamma(x, shape=2, scale=2)) Duncan Murdoch
Thank you very much for the answer! However, instead of x being some uniform values, I have real values. Hence, if I have dat$V1 of my interest, formula should be like this: qqmath(~ V1, data=dat, distribution=function(V1) qgamma(V1, shape=gammafit(dat$V1)$shape, scale=gammafit(dat$V1)$scale)) Is that correct? (gammafit() from mhsmm package calculates parameters of gamma function) Thank you, again. Best, PM Duncan Murdoch wrote:> On 9/4/2009 8:36 AM, Petar Milin wrote: >> Hello ALL! >> Can anyone tell me how to specify qqmath() function with distribution >> qgamma? >> In help it is bit vague how to pass shape and scale parameters for gamma. > > Take a look at the first example, which passes in the df parameter for a > t distribution. You want something like > > x <- runif(1000) # not a gamma, plot should look bad > qqmath(~ x, distribution=function(x) qgamma(x, shape=2, scale=2)) > > Duncan Murdoch >
You should pay close attention to the definitions of the parameters
passed to the various gamma functions.
x <- rgamma(1000, 2, 2)
library(mhsmm)
qsh <- gammafit(x)$shape; qsc <- gammafit(x)$scale
> qsh
x
x 2.009260
> qsc
x
x 0.4827448
On Sep 4, 2009, at 11:59 AM, Petar Milin wrote:
> Thank you very much for the answer!
> However, instead of x being some uniform values, I have real values.
> Hence, if I have dat$V1 of my interest, formula should be like this:
>
> qqmath(~ V1, data=dat, distribution=function(V1) qgamma(V1,
> shape=gammafit(dat$V1)$shape, scale=gammafit(dat$V1)$scale))
>
> Is that correct?
> (gammafit() from mhsmm package calculates parameters of gamma
> function)
>
> Thank you, again. Best,
> PM
>
> Duncan Murdoch wrote:
>> On 9/4/2009 8:36 AM, Petar Milin wrote:
>>> Hello ALL!
>>> Can anyone tell me how to specify qqmath() function with
>>> distribution qgamma?
>>> In help it is bit vague how to pass shape and scale parameters for
>>> gamma.
>> Take a look at the first example, which passes in the df parameter
>> for a t distribution. You want something like
>> x <- runif(1000) # not a gamma, plot should look bad
>> qqmath(~ x, distribution=function(x) qgamma(x, shape=2, scale=2))
>> Duncan Murdoch
>>
>
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